Exam 10: The Hypothesis of Difference

A researcher was interested in studying the possible deterrent effect of sentencing. A sample of 12 recidivists was compared with another sample of 12 who had stayed clean. Both groups had been convicted of distributing drugs and both groups had served time. For each subject the length of the previous sentence in months was found. Non-Recidivists Recidivists 36 60 48 72 54 59 32 35 66 56 45 55 37 42 46 57 35 60 42 64 28 97 24 28 -Identify the independent variable.

The Levene test assesses the degree of skewness in both distributions.

If the Levene test resulted in a significance level greater than .05, then homogeneity of variance can be assumed.

A researcher selects a pair of random samples and predicts beforehand that Group 2 will score higher than Group 1. The scores in Group 1 are 11, 10, 8, 3, 7, 1. The scores in Group 2 are 12, 11, 8, 4, 9, 2. a. Find the t ratio b. As a one-tail t, should Ho be rejected? If rejected, state the probability of the alpha error. c. Do the two groups represent a single population?

A researcher selects a pair of random samples. In Group 1 the scores are 12, 6, 9, 10, 8, 7. In Group 2, the scores are, 10, 4, 7, 8, 7, 6. Find the standard error of difference.

A researcher selects a pair of random samples. In Group 1 the scores are 14, 10, 10, 9, 8, 6, 4. In Group 2 the scores are 12, 10, 6, 5, 4, 2, 2. a. Find the t ratio b. As a two-tail t, should Ho be rejected? If rejected, state the probability of the alpha error. c. Do the two groups represent a single population?

A researcher selects a pair of random samples. In Group 1 the scores are 25, 25, 24, 24, 23, 233, 22, 21, 20. In Group 2 the scores are 22, 20, 20, 18, 15, 15, 12, 12, 10. a. Find the t ratio b. Do you reject Ho? c. Do the two groups represent a single population?

The larger the effect size, the greater the likelihood of detecting population difference with inferential statistical tests.

A researcher was interested in studying the possible deterrent effect of sentencing. A sample of 12 recidivists was compared with another sample of 12 who had stayed clean. Both groups had been convicted of distributing drugs and both groups had served time. For each subject the length of the previous sentence in months was found. Non-Recidivists Recidivists 36 60 48 72 54 59 32 35 66 56 45 55 37 42 46 57 35 60 42 64 28 97 24 28 -Did the results answer the researcher's question?

If the tabled value for t, for a certain number of degrees of freedom, were 3.17, and the calculated value of t were 3.17, then

Since psychopaths account for a quarter of all prisoners in the United States (and for as much as 50% of all violent crime) researchers have been examining the personality traits that may play a role in this condition. Tow groups of inmates, half diagnosed by Psychiatrists as psychopathic and the other not so diagnosed were given the IRI (Interpersonal Reactivity Index as a measure of empathy). The scores, converted to T scores were as follows: Psychopaths: 35,40,28,44,45,48,42,38,40,44. Non-Pychopaths: 52,60,50,48,55,50,54,55,44,40. -Identify the dependent variable.

Whenever the alternative hypothesis is written as "mean 1 is greater than mean 2", then

According to the text, the value beyond which alpha should not be set, is

In order to use the estimated standard error of difference for making probability estimates, both samples must

Every degree of freedom value specifies

For the t ratio, when the null hypothesis is rejected, then

If the mean of the distribution of differences were to equal -6.00, this would indicate that

When graphing the distribution of differences, the ordinate is used to represent

The estimated standard error of difference may never assume a negative value.

A group of 20 violent drug abusers, all of whom had committed homicide while under the influence of a psychostimulant, was selected from the population of a certain prison. Half the men had been cocaine abusers while the other half had been on methamphetamines. All were abstinent at the time of testing. The men were tested on the CAQ (Clinical Analysis Questionnaire) and their Factor Q1 scores were compared (Factor Q1 includes Radicalism, Hypochondriasis and Boredom & Withdrawal). Their scores, converted to T scores, were as follows: Cocaine Group: 65,58,65,62,60,61,70,71,68,75. Methamphetamine Group: 60,53,52,55,54,59,62,60,60,56 -Do the two groups differ significantly?