Question

4.   For the following problems, indicate what the independent variable (IV),
   dependent variable (DV), null hypothesis (Ho), alternative hypothesis (HA), and
   the appropriate statistical test would be (t-test for independent samples, t-test for
   dependent samples, ANOVA). (15 Pts)

   a.   Since muscle tension in the head region is associated with tension headaches,
you reason that if you can reduce tension you will reduce headaches. You
   design an experiment in which 9 subjects with tension headaches participate.
The number of tension headaches in one week is recorded. The 9 subjects are
then taught relaxation techniques. After training, the number of tension
headaches in one week are recorded again. Did the relaxation technique affect
the number of tension headaches?

IV _________________________       DV __________________________

Ho: _______________________       HA: __________________________

       Appropriate Statistical Test: __________________________________________  

   b.   A researcher is interested in determining the possible side effect of shock on memory of verbal material. Subjects are randomly selected and then randomly assigned to one of three treatment conditions. Group A receives no shock, Group B receives medium shock, and Group C gets high-intensity shock levels. The various shock levels are introduced during the learning period. All subjects then take a verbal retention test, with high scores indicating more retention. Is there a difference among the 3 groups?

IV _________________________       DV __________________________

Ho: _______________________       HA: __________________________

Appropriate Statistical Test: __________________________________________

c.       A researcher is interested in whether a certain hour-long film that portrays the insidious effects of racial prejudice will affect attitudes toward a minority group. Two groups of 31 subjects each were randomly selected and randomly assigned to one of two conditions: Group A watched the movie, and Group B spent the hour playing cards. Both groups were then given a racial-attitude test, wherein high scores represented a higher level of prejudice. Did the film make a difference?

   IV: _________________________   DV: __________________________

   Ho: _______________________       HA: __________________________

           Appropriate Statistical Test: ________________________________

Answer 1

Dependent variable : Number of tension headaches in week .

Independent Variable : Muscle tension in head region

Since headaches is dependent on muscle tension , headache is dependent and muscle tension is independent.

Now we want to test whether average number of headaches in week is different for people with muscle tension and people who are relaxed

Null hypothesis : Average number of headaches for people with muscle tension is equal to Average number of headache without muscle tension

Alternative hypothesis : Average number is more for people with muscle tension ( what if you Reject Null , what you want to conclude is alternative hypothesis )

Statistical test : Paired sample t test .

T test because we are testing difference in means and sample size is small. It is paired t test because samples are dependent . You are recording score for person having muscle tension and you record score of same person after giving relaxation . If you have 18 observation values 09 each ( before relaxation and after relaxation ) are generated based on 09 subjects . Had it been independent t test number of subjects could have been 18 .

b) Independent Variable: Shock treatment .

dependent Variable : Verbal Retention test score.

Verbal Retention is dependent on shock received .

Null hypothesis : Average Verbal Retention test score is same for all 3 groups . ( Verbal Retention score is not affected by shock treatment )

Alternative hypothesis : Average Verbal Retention test score differs across at least one of the pairs . ( Verbal Retention score Varies on intensity of shock)

We are testing if mean of all three groups is same or not .

To test mean of three or more groups across levels of one independent variable we Use One way ANOVA

Statistical test used : ONE way ANOVA.

c) Independent Variable is racial prejudice

Dependent Variable : Attitude toward minority groups( this is measured using racial attitude test scores)

Null hypothesis : Mean score of racial prejudice is same for group A and group B .

Alternative hypothesis : Mean score is more for people who watch movie ( people who are exposed to racial prejudice have more racist attitude than people who are not exposed)

Statistical test : Two sample t test ( independent sample t test)

Two sample t test is used to test mean of two independent samples . See there are 31 pairs of observations and 62 subjects ( 31 in each group ) .