# Statistics 2

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- Created by: Shannon
- Created on: 13-02-16 13:18

What does the research design affect?

Which statistical test you use

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When will the research design change?

If you are finding a difference or a relationship

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What is correlational design?

Investigates whether a relationship exists between two variables

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Which correlational design is used if data is normally distributed?

Pearsons' product moment correlation (r)

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Which correlational design is used when data is NOT normally distributed?

Spearman's Rho Correlation Coefficient

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What is an experimental design?

Used to investigate whether a difference exists between two variables

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What is an independent variable?

Manipulated

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What is a dependent variable?

Measured

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What is an extraneous variable?

May have an impact on our other variables

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What three criteria's does an Experiment have to satisfy in order for it to be a TRUE EXPERIMENTAL DESIGN?

- Experimental manipulation - Standardisation of procedures - Random allocation of participants to IV conditions

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What is random allocaiton?

Each possible outcome has an equal chance of being picked

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What is Quasi-Experimental?

When all 3 criteria's can't be met

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What is a directional hypothesis also known as?

One tailed

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What is a non-directional hypothesis also known as?

Two-tailed test

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What is a one-tailed test?

Specifies the direction of the relationship between the variables

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What is a two-tailed test?

No direction of the relationship or difference is predicted

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What is 0.05? (1 in 20 chance)

The probability that something will happen by chance - statistically significatn

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If we raised the probability to 0.1 what type of error would we find?

Type 1 Error - Find effects that are not there

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If we lowered the level to 0.01 what type of error would we find?

Type 2 Error - We would miss genuine effects

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What does it mean if the bars DO NOT overlap in error bars?

A real difference between the population means

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What does it mean if the bars DO overlap in error bars?

Suggest no real difference between the population means

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What is a WITHIN PARTICIPANT DESIGN?

If participants take part in more than one condition (related sample)

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What is a BETWEEN PARTICIPANTS DESIGN?

If participants only take place in one condition (Independent samples)

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What is a MIXED DESIGN?

A combination of within and between factors - More than 1 IV is needed

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What are the 2 advantages of WITHIN PPT DESIGN?

- Fewer ppts required - greater control over confounding variables e.g. individual differences

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What are the 2 advantages of BETWEEN PPT design?

Removes the chance of practice or fatigue effects - Harder for ppts to guess the purpose of the study

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What are the 2 disadvantages of WITHIN PPT DESIGN?

Increased chance of practice or fatigure - incerased chance of ppt guessing the study = demand characteristics

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What are the 2 disadvantages of BETWEEN PPT DESIGN?

More ppts required - Not much control over confounding variables - individual differences

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What do T-test show?

If there is a significant difference between the means of 2 conditions

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What is the independent (unrelated) t-test?

Calculates whether the mean scores from 2 different groups are significantly different

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When does independent t-test work best?

When score is normally distributed

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What does the independent t-test use?

Means from two different samples of ppts

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When do you NOT use an unrelated T-test?

When you have 3 or more groups of ppt

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What test should you use

ANOVA

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When do you use a RELATED t-test

If you have 2 sets of scores from one group of ppts

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What is a paired t-test?

Paired

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What is the formula for T-test

Difference between group means (M1-M2) / Variability of groups (Measure of spread within groups) - See sheet

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The higher the T- value....

The bigger the difference - less likely to accept null hypothesis

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What does the T- value tell us?

About the size of the difference (magnitude)

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What is the issue with selecting a sample from a population?

We can't be certain how representative it is of the population

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Why is this a disadvantage?

We don't use all members of the population therefore isn't entirely accurate

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What is sampling errors?

The degree to which the population parameter differs from the sample statistics

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What does a larger sample mean?

Smaller sampling error

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What does a smaller sample mean?

Larger sampling error

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What is the null hypothesis for a t-test?

No significant difference between two means

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If the population means are the same what is the sampling distribution

Zero

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If there is no difference between our means what would we expect the t-value to be?

Closer to the middle region of the sampling distribution

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What do t-tests help us calculate?

How far from zero the difference between the two obtained means is

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The higher the t-value

The more likely it is that any difference between the group means is not the result of a sampling error

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What is the degrees of freedom in an Independent t-test?

n-1 for both groups

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What does a related t-test test?

Whether one mean is significantly different from another

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What are the two sources of variation?

Variation due to the difference between the means (IV) and Variation due to uncontrolled factors (Error Variance)

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How can we reduce Error variance?

By measuring the same thing twice as individual differences are removed

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When do you use related t-test?

Single group of ppts that are measured twice or are matched into pairs

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When don't you use related t-test?

When you have two sets of scores from a single group of participants on different measures

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Give an example

If you took extraversion and intelligence

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What is a One-Way ANOVA?

An extention of the t-test

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When is a One-Way ANOVA used?

When we have three or more groups of participant (Still 1 IV and 1 DV)

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How many levels does the IV have?

2 (groups of participants)

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What does an ANOVA do?

Comapres the between group variance with the within groups variance

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What is the F-ratio

Between groups variance (variance due to IV) / Within groups variance (Error variance)

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Within groups...

Variance is minimal

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Between groups...

Variance is larger

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The larger the between groups variance in relation to the within groups variance...

The larger the F ratio

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What does it mean if the F ratio is small?

The within-groups variance is larger than between groups

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What does it mean if the F ratio is large?

The within-groups variance is smaller than between groups

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What does the null hypothesis state?

That there is no difference among the means (between groups)

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What will the F value be if the null hypothesis is true?

1

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If the between groups variance is larger than the within groups variance what does this mean?

The IV has an effect therefore the ratio will be greater than 1

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What is the significance level?

0.05

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What is a Type 1 error?

1 in 0

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What happens if you increase the number of tests on the same data?

The chance of finding a significant result by chance is increased

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When can't you use a one way anova?

When there is more than 1 IV

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What ANOVA do you use instead?

A factorial ANOVA

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IVS = Factors

Conditions = LEVELS

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What are the four sources of variance

1. Main effect of factor 1 2. Main effect of factor 2 3. The interaction between Factor 1 and Factor 2 4. Error variance

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What is the main effect of factor 1/2?

The effect that one factor has on the DV, irrespective of the other factor

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What is the interaction between factor 1 and 2

The ways in which factor 1 interacts with factor 2 - behaves differently

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What are the three significant test?

3 Hypothesis = 2 main effects and 1 interaction

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How does two way anova interpretation begin?

With examination of the interaction

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ANOVA terminology

Check revision sheet

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What does the number of numbers show?

The number of factors (IVs)

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What do the numbers themselves represent?

The levels in each of the factors

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When is anova USED?

When we want to analyse all the possible sources of variance in a study

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Parallel line in a graph shows

No interactio

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No parallel lines on a graph

Possible interaction

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Lines cross on a group

Interection

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When is a Post Hoc used?

After insepcting the ANOVA results

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What does a Post Hoc do?

Compare every mean with every other mean

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What does every significant outcome mean?

The means are different and tells us where the differences in the ANOVA actually are

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When do you perform a post hoc

If results of your ANOVA were significant and if you have more than 2 levels of factors

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What does TUKEY'S HONESTLY SIGNIFICANCE DIFFERENCE DO?

Controls the type 1 error rate well

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## Other cards in this set

### Card 2

#### Front

When will the research design change?

#### Back

If you are finding a difference or a relationship

### Card 3

#### Front

What is correlational design?

#### Back

### Card 4

#### Front

Which correlational design is used if data is normally distributed?

#### Back

### Card 5

#### Front

Which correlational design is used when data is NOT normally distributed?

#### Back

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