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# Population has average weight of 71kgs. Compute a test statistic.

Suppose a population has average weight of 71 kgs. A sampling of that population resulted in the following weights:
Weights in kgs
60
62
65
68
69
69
71
72
75
77

c. Find a 95% confidence interval for this sample of data.
d. State a null hypothesis comparing the average weights of this sample with the average weights of the population.
e. If we were to test the null hypothesis you created in part d, which test statistic would you use (hint: there are only two test statistics introduced in chapter 4) and explain why?
f. Assuming you use a two tailed test with a 5% significance (a) level, what is the critical value for this test statistic? Show your reasoning.
g. Compute the test statistic and report it. Determine if we should accept or reject the null hypothesis.

#### Solution Preview

c) Confidence interval

The formula would be: C. I. = M ± (z * SE)
Where:
m=mean
z = the degree of alpha - we get it from a z-table: http://www.statsoft.com/textbook/sttable.html#z
SE = standard error = standard deviation / square root of sample size

So our mean is the sum of all the values/ sample size: 68.8
95% confidence would be an alpha of 0.05.

How do we get this? We need to find the area under the curve first. We take the entire bell curve of 1. We divide in half, and it is 0.5. So 1 - 0.5 is 0.5. ...

#### Solution Summary

The test statistics if calculated for the population average weight.

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