Probability and Distributions

Question 1

Define normal distribution

Answer 1

When data is symmetrical around central scores and the mean, median and mode are equal

Question 2

What is a Gaussian Curve?

Answer 2

Normal distribution

Question 3

What does a positive skew look like?

Answer 3

The peak is on the left hand side

Question 4

What does a negative skew look like?

Answer 4

The peak is on the right hand side

Question 5

How would you calculate Pearson’s coefficient of skew?

Answer 5

skew = 3(mean - median) / standard deviation

Question 6

If the skew is <0, what is the data?

Answer 6

Data is negatively skewed

Question 7

If the skew is >0, what is the data?

Answer 7

The data is positively skewed

Question 8

How can you test for distribution?

Answer 8

Normality tests

Question 9

From the mean and standard deviation of the data alone, what can we predict?

Answer 9

We can predict the value of y for any value of x

Question 10

What test would you use for one-sample, independent and paired?

Answer 10

T-test

Question 11

What test assumes values e.g. the mean and SD accurately reflect the population distribution?

Answer 11

Parametric tests

Question 12

What can transforming data into Z scores help?

Answer 12

Helps standardise data and reduce the impact of skewness

Question 13

What equation would you use when transforming data into Z scores?

Answer 13

Z = individual point - group mean / standard deviation

Question 14

What does a Z score tell us?

Answer 14

Tells us how many standard deviations someone was from the mean

Question 15

What are some pros of Z scores?

Answer 15

Can transform data to a standardised table and can compare things relative to their own population

Question 16

What can we estimate about a population based on a sample?

Answer 16

Values and statistics

Question 17

Define sampling error

Answer 17

The value is likely to differ from the true mean of the global population (or other samples)

Question 18

What can we use to say how confident we are that our sample values represent the population?

Answer 18

Use the Standard Error of the mean

Question 19

What is the equation for Standard Error?

Answer 19

SEM = Standard deviation / square root of number of datapoint

Question 20

What does the Standard error tell us?

Answer 20

How likely it is our sample will vary from one sampling to another

Question 21

What are the Standard error’s biggest influences?

Answer 21

Variability of the original data

Question 22

What would someone use instead of the Standard error?

Answer 22

Confidence intervals

Question 23

Define confidence intervals

Answer 23

The range of values that, in a certain proportion of samples, contains the true value of a statistic

Question 24

What is the visual for confidence interval on a graph?

Answer 24

Error bars