# Project #8908 - Z scores and confidence interval

1. The following is a set of approximately normal scores given on the Zwiebecker Mental Aptitude Test by a fourth grade class. For the purpose of this lab, these scores will be considered a complete population, rather than a sample.

```         22  84  48  66  72  63  30  40  45  68  61
```
```         54  52  53  50  43  76  53  34  38  56  58
```

a. Plot a frequency distribution of these scores.

b. Compute the mean.

c. Compute the standard deviation

1. What percentage of scores should fall between the mean and 65, granted that the data are normal?

2. How many scores should fall between the mean and 48?

f. What percentage of scores should fall below 35?
g. What percentage of scores should lie between 50 and 60? h. Three percent of the scores should lie above: _______

2. Assuming that the above set of data were a sample from a population, find the 95% confidence interval on the mean.

3. What is the 99% confidence interval (using the same data)?

4. Assume that we cannot tolerate this interval width. If all else remains the same, what change in N would reduce this interval to 1/4 its size?

 Subject Mathematics Due By (Pacific Time) 07/11/2013 12:00 pm
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