BIOL132 - L2

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  • Created by: Katherine
  • Created on: 07-06-16 16:36
What are variables?
They are a class of outcomes that can take on more than one value. The more precisely a variable is measured, the more useful the measurement is.
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What are the two types of variable?
Dependent and Independent
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What are dependent variables?
The outcomes of a research study, depend on the experimental treatment
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What are the independent variables?
Treatments of conditions under control of te researcher. Levels - at least two different values of the independent variable must be present.
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What are examples of the independent variable?
Age, social class, gender
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What is an example of the dependent variable?
Values based on the independent variable
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What is accuracy?
The closeness to the actual (true) value, depends on who is measuring it
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What is precision?
It is how close together the measurements are. It depends on the measurement tool
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What are descriptive statistics? Basic measures
Avergae score on a variable, how different scores are from one another
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What are inferential statistics - help make decisions about:
Null and research hypotheses. Generalizing from sample to population
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What is the mean?
Arithmetric average
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What is the median?
Midpoin in a distribution
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WHat is the mode?
Most frequent score
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How is the mode calculated?
Add up all the scores and divide the total by the number of values
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How is the median calculated when N is odd?
Order scores from lowest to highest, count nmber os scores. select middle score
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How is median caclulated when N is even?
Order scores from lowest to highest, count number of scores, compute mean of the two middle scores.
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What is the mode?
The most frequently occuring score
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The mean and median of data from a symmetric distribution should be close together. True?
Yes - the actual mean and median of a symmetric distribution are exactly the same
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In an asymmetric/skewed distribution, the mean is farther out in the long tail than is the median - true?
Yes - the mean is pulled in the direction of the possible outlier(s)
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So, should the mean or median generally be used in asymmetric distribution?
The median
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Is the median affected by extreme values?
No - it is resistant
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Is the mean affected by extreme values?
Yes
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When do you use the mean?
Inverval and ration - use when you can, and the data fit. E.g. speed of response, age in years
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When do you use median?
Ordinal - when data include extreme scores. e.g. Rank in class, birth order, income
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When do you use the mode?
Nominal, use when data are categorical. E.g. eye colour, party affiliation
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What is the range?
Difference between highest and lowest score
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What is standard deviation?
Average difference of each score from the mean
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What is variability?
It is the degree of spread or dispersion in a set of scores.
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How do you work out standard deviation?
S = Summation sign (each score - mean) / size of sample - 1
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What shape is the normal curve?
Bell shaped
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What are features of the normal curve?
Mean = medium = mode, symmetrical about midpoint. Tails approach X axis,b but don't touch
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What are quartiles?
3 numbers which divide the ordered data into 4 equal sized groups.
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What does the q1 have?
25% of data below it
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What does q2 have?
50% of data below it (median)
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What does the q3 have?
75% of data below it
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How do you work out the quRTILES?
Order the data, for q2, just find the median. For q1, look at the lower half of the data values, those to the left of the median. Find the median of this lower half. For q3, find the median for the upper half
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What is the IQR?
Q3 - Q1
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What doe the lines on the box plot show?
The min and the max value
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What is used to represent descriptive data?
Statistical summaries, graphs, pie charts, histograms, stem and leaf plots, quartile ranges. Each method of depiction will suit a particular type of data.
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Other cards in this set

Card 2

Front

What are the two types of variable?

Back

Dependent and Independent

Card 3

Front

What are dependent variables?

Back

Preview of the front of card 3

Card 4

Front

What are the independent variables?

Back

Preview of the front of card 4

Card 5

Front

What are examples of the independent variable?

Back

Preview of the front of card 5
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