Question

The accompanying data table lists measured voltage amounts supplied directly to a family’s home. The power supply company states that it has a target power supply of 120 volts. Using these home voltage amounts, test the claim that the mean is 120 volts. Use a 0.05 significance level.
Calculate the test statistic. Information below..
Day Volts Day Volts
1 124.5 21 124.0
2 123.9 22 123.9
3 123.9 23 123.6
4 123.8 24 124.2
5 123.4 25 123.4
6 123.3 26 123.4
7 123.3 27 123.4
8 123.6 28 123.4
9 123.5 29 123.3
10 124.1 30 124.4
11 123.5 31 123.5
12 123.7 32 123.6
13 124.1 33 123.8
14 123.7 34 123.9
15 123.9 35 123.9
16 124.0 36 123.8
17 124.2 37 123.9
18 123.8 38 123.7
19 123.8 39 123.8
20 123.8 40 123.8

Answer 1

Find the mean first = sum of scores/number of scores

Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.

Standard deviation = square root of variance

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n

If only one SD is provided, you can use just that to determine SEdiff.

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability
related to t he Z score.

I'll let you do the calculations.