# Statistics: In a study published in the American Journal of Psychiatry, researchers wanted to measure?

) In a study published in the American Journal of Psychiatry, researchers wanted to measure the effect of alcohol on the development of the hippocampal region in adolescents. The hippocampus is the portion of the brain responsible for long-term memory storage. The researchers randomly selected 12 subjects with adolescent-onset alcohol use disorders to test the claim that hippocampal volumes in alcoholic adolescents were less than the normal volume of 9.02 cubic centimeters. An analysis of the sample data revealed that the hippocampal volume is approximately normal with mean 7.9 and standard deviation=.72. Use the .01 level of significance.

a. State the null and the alternate hypotheses.

Ho: ___________________ and Ha: ___________________

b. State the critical value(s) for this test. ________________

c. Find the test statistic. ___________________

d. Approximate the p-value for this test. ______________________

e. State your conclusion in the context of this problem. ____________________

Please show all work

Thank you

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### 2 Answers

- paramvenuLv 79 years agoFavorite Answer
a) Ho: Mu >/= 9.02

Ha: Mu < 9.02 (left tailed test)

b)t-test is the test criterion being n < 30

Degrees of freedom = v = n-1 = 12-1 = 11

Level of significance = alpha = a = 0.01

Critical value of t for v = 11 at a = 0.01 is 2.718

c) Test statistic = t = (Xbar - Mu)*sqrt n / S

Xbar = Mean of the sample = 7.9

Mu = Mean of the population = 9.02

n = Sample size = 12

S = Standard deviation of the population = 0.72

Calculated t-value = (7.9-9.02)*sqrt 12/0.72 = - 5.389

d)

e) Since the calculated value of t (5.389) is > the critical value of t (2.718), the Ho will be rejected. In other words the Ha will be accepted.

It can be inferredd that the claim that hippocampal volumes in alcoholic adolescents were less than the normal volume of 9.02 ccms.

- Anonymous5 years ago
I read the abstract from the original source. Important to note is the fact that the study is based -solely- on 371 in-patients who are clinically depressed. This is too narrow to arrive at any general conclusions about society. For example: how many religious people never go to a psychiatrist? I believe that most religious people who get depressed talk to their minister/preacher/priest rather than check into a clinic. Wouldn't you agree? So how many commit suicide after talking to their ministers? This study doesn't look at that. 371 in-patients does not represent general trends in America. That's what I think.