# Compute the z or t value of the sample test statistic.

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• December 21st 2008, 05:35 PM
mathretard
Compute the z or t value of the sample test statistic.
In an article appearing in Today’s Health a writer states that the average number of calories in a serving of popcorn is 75. To determine if the average number of calories in a serving of popcorn is different from 75, a nutritionist selected a random sample of 20 servings of popcorn and computed the sample mean number of calories per serving to be 78 with a sample standard deviation of 7.
• December 21st 2008, 05:44 PM
mr fantastic
Quote:

Originally Posted by mathretard
In an article appearing in Today’s Health a writer states that the average number of calories in a serving of popcorn is 75. To determine if the average number of calories in a serving of popcorn is different from 75, a nutritionist selected a random sample of 20 servings of popcorn and computed the sample mean number of calories per serving to be 78 with a sample standard deviation of 7.

Where is the trouble in calculating t?

You substitute the given values into the formula $t = \frac{\overline{x} - \mu_0}{s/\sqrt{n}}$.
• December 21st 2008, 05:51 PM
mathretard
additional question
So is the answer t= 1.916 or z=1.916
• December 21st 2008, 05:58 PM
mr fantastic
Quote:

Originally Posted by mathretard
So is the answer t= 1.916 or z=1.916

You cannot use z because the population variance is unknown and the sample size is small.

I haven't checked the answer - I assume you can correctly use a calculator.