Stats

Question 1

Graphical methods of presentation(x5)

Answer 1

• scatter plot
• bar chart
• histogram
• mean +/- s/d
• box plot

Question 2

When would the median and mode be different to the mean value?

Answer 2

Small samples and skewed distributions (non-normal)

Question 3

When can the t-test be employed?

Answer 3

When the data (raw/transformed) follow a normal distribution

Question 4

Response if P

Answer 4

Difference is significant – reject null hypothesis

Question 5

Response if P>critical value

Answer 5

Cannot reject null hypothesis

Question 6

Box and whisker plot: what are the values represented within the box?

Answer 6

Values between the 25th and 75th percentile

Question 7

Box and whisker plot: what do the whiskers represent?

Answer 7

Whiskers show the range of data

Question 8

What is the type I error?

Answer 8

False positive result; rejection of the null hypothesis when it is true

Question 9

In what instances is it likely to cause a type I error?

Answer 9

Rejection of null hypothesis when p-value is close to 0.05

Question 10

What is type II error?

Answer 10

Not rejecting the null hypothesis when it is false; might erroneously conclude that no effect is present when there actually is

Question 11

Factors affecting the power of a stats test (x4)

Answer 11

• sample size
• variability of observations
• effect of interest
• significance level desired

Question 12

Which test is used to avoid the problem of multiple corrections?

Answer 12

Global test - ANOVA (analysis of variance)

Question 13

What do you do if the ANOVA test yields a significant result (ie if P

Answer 13

Move to other tests e.g. Post-hoc tests - bonferroni, scheffe

Question 14

When is non-parametric stats used? (X2)

Answer 14

• when normality cannot be assumed

- categorical data

Question 15

How is the Mann Whitney test used?

Answer 15

The individual data scores are converted into ranks for any subsequent analysis

Question 16

What is the non-parametric alternative to the paired t test

Answer 16

Wilcoxon signed rank test

Question 17

What is the global test used in non-parametric stats?

Answer 17

Kruskal-Wallis

Question 18

What is the correlation analysis?

Answer 18

The degree of association between two variables

Question 19

How is data presented in correlation analysis?

Answer 19

Scatter plot

Question 20

What’s on the x and y-axis of the scatter plot?

Answer 20

X-axis: independent variable

Y-axis: dependent variable

Question 21

What does pearson’s correlation coefficient measure?

Answer 21

The degree of linear association between two variables

Question 22

Range of values of the pearson’s correlation coefficient

Answer 22

-1 to +1 (sign indicates the direction of association)

Question 23

In what cases will Pearson’s ‘r’ value be misleading? (X3)

Answer 23

• non-linear r/s
• presence of outliers
• presence of subgroups

Question 24

When do you not use pearson’s? (X3)

Answer 24

• if one variable is on the ordinal scale
• if x or y are not normally distributed
• if the sample size is too small

Question 25

What should be used in cases when pearson’s correlation coefficient is not used?

Answer 25

Spearman’s rank of correlation

Question 26

What is the coefficient of determination?

Answer 26

It determines how well the regression line accounts for variability in the dependant variable

Question 27

Ways of presenting data (x2)

Answer 27

Table

Graph