W8: Data Analysis II

Question 1

What are tests of significance? Give examples.

Answer 1

to test hypotheses
eg. chi square, t-test, ANOVA

Question 2

What is a research (alternative) hypothesis, Ha?

Answer 2

prediction of relationship between variables

Question 3

What is a null hypothesis, Ho?

Answer 3

prediction that there is no relationship between variables (by convention, this is a statement of equality)

Question 4

Which hypothesis is tested in a test of significance?

Answer 4

the null hypothesis is tested

Question 5

What does it mean to accept the null hypothesis?

Answer 5

conclude that there is no difference (no relationship) between variables

Question 6

What does it mean to reject the null hypothesis?

Answer 6

conclude that there probably is a difference (relationship) between the variables

Question 7

what is another way to say “accept the null hypothesis”

Answer 7

fail to reject the null hypothesis

Question 8

What is publication bias? What are the impacts?

Answer 8

occurs if results from studies which have not been published are different from those that are published

impacts interpretation of reviews and meta analyses that include only published literature; overestimation of effects of treatment

Question 9

(analysis with multiple variables) Define the main effect.

Answer 9

differences among groups for a single IV that are significant, temporarily ignoring all other IVs

Question 10

(analysis with multiple variables) define interaction effects.

Answer 10

differences among groups of a single IV that are predictable only by knowing the level of another IV

Question 11

what is the difference between a one and two tailed test?

Answer 11

one tail: specifies direction of a relationship in advance (“directional” hypothesis)- if you predict direction of a relationship in advance, you do a one tailed test

two tailed test: test of any relationship between variables, regardless of direction of relationship
- if you do not predict direction of relationship, you do a two tailed test

Question 12

what are sampling fluctuations?

Answer 12

how much stat value fluctuates from sample to sample.

Not reflective of true difference in population from which sample was selected

Question 13

what is statistical significance? What type of error can occur?

Answer 13

degree of risk that you are willing to take that you will reject a null hypothesis when its actually true
-> concluding that there’s a stat. sig. difference exists when there is actually no difference
(type one error) = level of statistical significance

Question 14

What is the difference between statistical and clinical significance?

Answer 14

clinical difference-> importance of a difference; decided by clinical expertise
stat significance-> says nothing about actual magnitude or importance of difference

Question 15

What are the three tests of significance?

Answer 15

1. Chi- square, X2
2. T-tests
3. ANOVA (extension of t-tests)

Question 16

When is chi-square used? What types of data are the DV and IV? What is the null hypothesis?

Answer 16

used with cross tabular analyses
IV: categorical (nominal/ordinal)
DV: nominal level
Ho: no significant difference between categories on variable of interest

Question 17

When is t-tests used? What types of data are the DV and IV? What is the null hypothesis?

Answer 17

compare means of 2 groups (means of DV); when sample size <30
DV: ratio level
IV: has two levels (categories) only

Ho: no significant difference between group means on variable of interest (dependent)

Question 18

What is the difference: between and within t-tests

Answer 18

between subjects t-test (2 independent samples): use in experimental design, with experimental and control group

within subjects t-test (2 dependent samples): same person subjected to different treatments and comparison is made between two treatments

Question 19

What is an analysis of variance (ANOVA)?

Answer 19

family of statistical tests- compares group means to assess whether differences across means are reliable

Question 20

What is a post hoc comparison?

Answer 20

comparison of differences across levels of an independent variable when results are significant

Question 21

What are the IV and DV in an ANOVA?

Answer 21

IV (treatment): 2+ categories (nominal/ordinal); can be more than 1 simultaneous IV
DV: measured at ratio level

Question 22

When are tests of significance not appropriate?

Answer 22

• access to total population
  -non-probability/random sampling procedures used
• high non-participation rate
• non experimental (qualitative) research
• when not guided by formal hypothesis
• when data set is limited

Question 23

What are inferential stats used for? What does it use for data analysis?

Answer 23

to determine probability that conclusion based on analysis of data from sample is true
- use tests of significance for data analysis