Stats assignment

Question 1

Research question

Answer 1

What influence does dissociative subtype of PTSD have on intensive trauma focused treatment program?

Question 2

hypothesis

Answer 2

-presence of dissociative subtype of PTSD have a detrimental effect on outcome of an intensive trauma focused treatment

Question 3

which method is used to recruit participants?

Answer 3

-convenience sampling
(= sample drawn from part of population that is close to hand)
-> participants were enrolled in clinical program

Question 4

What are the dependent and independent variables of the study?

Answer 4

independent: dissociative / not dissociative
dependent: outcome of treatment (Caps scores (pre and post treatment) and PSS- SR ( at day 1 and post treatment)

Question 5

What is the level of measurement for the different variables? (keywords: nominal, ordinal,
interval)

Answer 5

independent : nominal (dissociative / not dissociative)

dependent: quantitative , (outcome of treatment)
time: ordinal / interval

Question 6

Are these between- or within-subjects variables?

Answer 6

• independent: between subject variable (each person only in one condition)
• dependent: within-subject: 1 person, all conditions

time= within subject

Question 7

What type of study is this (observational study, correlational study, quasi-experiment,
experiment)?

Answer 7

quasi experiment -> no random sampling, observational study

Question 8

What statistical test was used to examine the hypotheses? (Keywords: one samples t-test,
independent samples t-test, paired samples t-test, (repeated measures/mixed design)
ANOVA, (repeated measures/mixed design) MANOVA, Chi-square test, linear regression)

Answer 8

• mixed design ANOVA

- > used to see whether 3 or more groups are different on dependent variable

Question 9

Did the authors statistically control for possible confounders? If so, which?

Answer 9

use of cohen’s d
-> compare baseline differences in age, gender, type of trauma

confounders= influences independet and dependent variable causal or not causal relationship
-> only possible control in experimental studies

Question 10

What are the values of the test statistics for the hypotheses and what are the corresponding
p-values? Are the results significant at a significance level of 5%? (keywords: t, F, Chi-
square)

Answer 10

Treatment outcome:

• CAPS: p=0,61 -> significant main effect of time
• PSS-SR: p=0,51 -> significant main effect of time

Impact of dissociative subtype:

• CAPS: p=0,4 -> main effect of group, no interaction
• PSS-SR: p=0,4 -> “

-> reduction in scores was the same for both scores

Question 11

interpretation

limitations

Answer 11

• you should not exclude people with DS from trauma-focused therapy
• > there is a main effect in treatment, but it doesn’t depend on subtype
• > H0 not rejected

limitations:
- external validity: useful for other studies?
- internal validity: trustworthy effect relationship between treatment and outcome?
- no homework
- insufficient follow up data
- dichotomization of dissociative subtype
- physical activity and trauma focused treatment

Question 12

random sampling

Answer 12

-entirely by chance

Question 13

systematic sampling

Answer 13

-sampling frame: every X individual

Question 14

stratified sampling

Answer 14

-population divided in subgroups who share characteristics

Question 15

quota sampling

Answer 15

-e.g. you select 10 men, 20 women and 10 children

Question 16

nominal, ordinal, interval , ratio

Answer 16

nominal: named variables
ordinal: named + ordered variables
interval: name + ordered + proportional interval between variables
rati: name + ordered + proportional interval between variables, can have absolut zero