SOLUTION: n a study published in the American Journal of Psychiatry, researchers wanted to measure the effect of alcohol on the hippocampal region, the portion of the brain responsible for l

Question 1198014: n a study published in the American Journal of Psychiatry, researchers wanted to measure the effect of alcohol on the hippocampal region, the portion of the brain responsible for long-term memory storage, in adolescents. The researchers randomly selected 12 adolescents with alcohol use disorders to determine whether the hippocampal volumes in the alcoholic adolescents were less than the normal volume of 9.02 cubic centimeters (cm3). An analysis of the sample data revealed that the hippocampal volume is approximately normal with mean 8.10 cm3 and standard deviation 0.7 cm3.
Fill in the blanks below regarding the conclusion of the appropriate hypothesis test:
At a 1% level of significance, the data PROVIDES OR DOES NOT PROVIDE sufficient evidence that hippocampal volumes in alcoholic adolescents ARE OR ARE NOT below the normal level.
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
test volume = 9.02 cubic centimeters.
sample mean = 8.10
sample standard deviation = .7
sample size = 12
t-score = (x - m) / s
x is the sample mean
m is the test mean
s is the standard error.
s = standard deviation of sample / square root of sample size = .7 / sqrt(12) = .2020725942.
t-score = (8.10 - 9.02) / s = -4.552819266.
the probability of getting a t-score with 11 degrees of freedom less than that is equal to .000413154.
this is significantly less than .01, or even .005.
the results of the test indicate that hippocampal volumes in alcoholic adolescents are strongly determined to be below the normal level.
the likelihood that the sample results are due to random variations in the mean of samples of the size indicated is extremely remote.
i confirmed by using an online t-test calculator.
the results are shown below:

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