# Statistics

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- Created by: Shannon
- Created on: 28-12-15 18:23

What is a Hypothesis?

A statement expressing the expected or predicted relationship between two or more variables

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What is a variable?

Anything that varies and can be measured

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What are Independent Variables?

A proposed cause. A predictor variable. A manipulated variable

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What is a dependent variable?

The proposed effect. An outcome variable. Measured not manipulated

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What is a level of measurement?

The relationship between what is being measured and the label/numbers that represent it

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What does the level of measurement tell you?

What test to use and how to present the data

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What is Nominal?

Category/Qualitative - Yes/No

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Give examples of Nominal data

Gender, Colours

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What is the test for Nominal data?

Chi-square

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What are the graphs for Nominal data?

Bar charts and Pie charts

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What are binary variables?

Only two categories. e.g. Yes/No

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What is Scale?

Score/Numerical/Quatitative

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Give examples of scale data?

IQ Score, Height, Weight

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What is the test for Scale data?

Pearson's correlation

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What are the graphs for Scale data?

Histograms/boxplots

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What is ordinal data?

Ordered/ranked

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What is the difference between Interval and Ratio data?

Ratio has an absolute zero whereas Interval doesn't

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Example of interval data

Temperature

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Example of ratio data

Height, Weight, Age

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What are descriptive stats?

Describes a data set by summarising and simplifying it

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What do do descriptive stats show?

Trends and patterns in data

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What are frequency distributions?

Tells us how many times a score or category occurs within our sample

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How many central tendencies are there?

6

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What is the mode?

Score that occurs more frequently

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What is bimodal distribution?

Two modes

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What is multimodal distribution

More than two modes

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How is the mode shown in a histogram?

Tallest bar

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What is the median?

The middle score when you put the scores in orer

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How do you calculate the median when there is an even number of scores?

Calculate the mean of the two middle scores

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What is the mean?

The total of all scores then divides by the number of scores

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Formula

See paper

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What is the range?

A measure of variability

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What does the range tell us?

The dispersion of the scores - how much spread there is

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How do you work out the range?

Take away the smallest score from the largest score

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What does the interquartile range tell you?

About the middle 50% of scores

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What is the 2nd quartile?

The median - splits the data set in two

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What is the lower quartile (Q1)?

The median of the lower half of the data set

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What is the upper quartile (Q3)?

Median of the upper half of the data set

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How do you work out the IQR?

Q3-Q1

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What are outliers?

Description of the data can be affected by extreme scores

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How do you work out outliers?

LQ-(IQR X 1.5) OR UQ + (IQR X 1.5)

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What should a normal distribution look like?

Symmetrical and the mean, median and mode should be located in the 50th percentile and are the same

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What is skew?

Whether scores tend to be higher or lower than the median

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What do skewed distributions look like?

Lack of symmetry, lopsided distribution, clustered at one end of the scale

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What does a negatively skewed distribution look like?

Left skewed/higher on the right/ tail on the left / mean and median to the left of the mode/ extreme scores of the lower end of the data

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What does a positively skewed distribution look like?

Right skewed/Higher on the left/ tail on the right/ mean and median on the right of the mode/ extreme scores on the higher end of the data

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What is a kurtosis?

The extent to which the scores are clustered around the mean or not

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What is leptokurtic distribution?

Positive kurtosis/ steep curve/ lots of scores in the tails/ pointy

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What us platykurtic distribution?

Negative kurtosis/shallow curve/ flatter than normal/ thin in the tails

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What is Variance?

Measure of the variability of scores

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The formula for variance

See paper

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What does variance show?

The difference between each score and the mean shows how much that score deviates from the average

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How to work out the variance?

1. Work out the mean 2. Take away the mean from each score then square it 3. Add up all the score-mean squared totals 4. Divide by how many scores there are in total

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How do you work out the standard deviation?

Square root the variance

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What is standard deviation?

The average amount by which scores differ from the mean or average score

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What is the formula for standard deviation?

See paper

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What does a small SD show?

The scores are close to the mean and so the mean is a good representation of the data

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How are large SD presented in a graph?

Flatter distribution

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How are small SD presented in a graph?

Pointy distribution

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What are Z-scores?

Represents the number of SD a score is from the mean

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How does you work out the Z-score?

Score - mean score / SD

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What does a large Z-score show?

The less typical a score is from the typical score within the sample

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What is the difference between SD and Estimated SD?

SD = looks at the SD in the actual data we collected / ESD = Generealises beyond the sample

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What is the formula for ESD?

Look on paper

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What is population?

Every member of the group

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What is a sample?

A collection of people who could represent the population

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What is Standard error?

Tells us how accurately a sample represents the population by

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What does a large SD show?

Lots of variation between samples therefore is NOT representative of population

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What is the formula for SE?

See paper

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What is sample mean?

The mean for each sample

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What is sampling variation?

Sample scores vary due to different members of the population

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What is sampling distribution?

Tells us the frequency distributions of sample means from the sample population

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What is a hypothesis?

A statement expressing the expected or predicted relationship between two or more variables

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What is a null hypothesis?

There is no difference or relationship

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What is an alternative hypothesis?

There is a relationship or difference

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What is a directional hypothesis?

States the direction of an effect/relationship

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What is a non-directional hypothesis?

Doesn't state the direction of an effect/relationship

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What are inferential stats?

infers something about the population based on what we have found within a sample

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What is probability

How likely it is that a score will occur?

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Formula for probability

See paper

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What is the p-value?

The probability of this event occurring if the null hypothesis is true

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When do you reject the null hypothesis?

at 0.05 or 5%

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When are the results not statistically significant?

when above 0.05 - accept null

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When are results statistically significant?

When below 0.05 - reject null

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What is Chi-square the test of?

Association

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What level of measurement data does Chi-square use?

Nominal

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What is c-s explore?

The relationship between two nominal variables

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Does C-S use scores or frequency counts?

Frequency counts

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What kind of design is c-s?

Between groups design

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What does c-s do?

Compare the frequency counts of two nominal variables

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What kind of table do you use for c-s?

Contingency/cross table

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What is residual?

The difference between observed and expected

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What is the formula for chi-square?

See paper

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The bigger the difference between the observed and expected frequencies...

The bigger the chi-square

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How is chi square presented?

See paper

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What is the degree of freedom?

The number of scores that are free to vary

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What are type 1 errors?

Thinking there is a genuine relationship when there isn't one / rejecting null when should reject alternative

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Whare type 2 errors?

Thinking there is no genuine relationship when there actually is / accepting null when should accept alternative

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What are effect sizes?

An objective and standardized measure of the size of an observed effect

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What does the effect sizes show us?

The magnitude of the difference between conditions of the strength of a relationship

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What statistical test can be used to calculate effect size?

Pearson's correlation coefficient

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What is statistical power?

The ability of a test to find a significant effect is one exists in the population // the probability of NOT making a type 2 error

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What does a bigger sample size // significance level // effect size show?

Greater power

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What does greater variability show?

Lower power

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Which graphs are used for nominal data?

Pie charts and bar charts

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Which graphs are used for scale data?

Histograms and boxplots

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Which graph to use for two score variables?

Scatterplot

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Which graphs to use for Nominal and Score data?

Table of means and SD // Bar chart showing means // multiple boxplots

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What are boxplots?

Show the range of scores and whether the data is symmetrical or skewed

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What do boxplots show?

Median // IQR // UQ and LQ // Most and least extreme scores // Outliers --> Look at diagram on paper

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What does the correlation coefficient lie between?

-1 and +1

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What is correlation coefficient (r)?

A ratio between covariance and a measure of each of the separate variances

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What is covariance?

Variance shared between 2 variables

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What does (r) indicate?

The strength and direction of a relationship between 2 variables

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What does the number between 0.00 and 1.00 show?

How much variation there is around best fit line

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What does r= 1 show?

Explains all variance // as one increases the other changes to proportionate amount

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What does r = 0 show?

Explains none of the variance // the increase of one variable does not lead to proportionate change

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What does the pearson correlation coefficent assume?

There is a straight line relationship between the variables

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How do you present the Pearson correlation?

r (df = n-2) = - .**, P = .**

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What is spearman's rho?

When data is not normally distributed or with ordinal data

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How to work out percentage variance?

r (squared) x 100

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What is regression?

Used to predict a score on a variable based on the score for another - 2 score variables

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What is the DV in regression?

The value to be predicted // criterion variable // Y

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What is the IV in regression?

Used to make the prediction // predictor variable // X

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What does regression tell us?

How much Y will change is X changes

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What is the formula for regression?

Predicted Slope (Y) = constant (a) + slope of regression line (B) x The score on the X axis from which we will predict the score on the Y axis (x)

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What does the constant tell us?

What point the regression line cuts the vertical line

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What does the slope of regression line tell us?

The change in the outcome associated with a unit change in the predictor

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What is the confidence interval?

Statistically derived interval estimate of a population parameter

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What is the point-estimate approach?

An alternative approach to inferential statistics

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What is point estimate?

Single figure estimate

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What is interval estimate?

A range within which we think that single figure will fall

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## Other cards in this set

### Card 2

#### Front

What is a variable?

#### Back

Anything that varies and can be measured

### Card 3

#### Front

What are Independent Variables?

#### Back

### Card 4

#### Front

What is a dependent variable?

#### Back

### Card 5

#### Front

What is a level of measurement?

#### Back

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