Question

Seven previously untrained males performed leg-strength training 3 days per week for 8 weeks (with four sets of five replications at 85% of one repetition maximum). Peak power during incremental cycling increased to a mean of 315 watts with a standard deviation of 16 watts. Construct a 95% confidence interval for the mean peak power after training.

Answer 1

The 95% confidence interval for the mean peak power after training is (283.64 watts, 346.34 watts).

Explanation:

We have that to find our
`\alpha` level, that is the subtraction of 1 by the confidence interval divided by 2. So:

`\alpha = (1-0.95)/(2) = 0.025`

Now, we have to find z in the Ztable as such z has a pvalue of
`1-\alpha`.

So it is z with a pvalue of
`1-0.025 = 0.975`, so
`z = 1.96`.

Now, find M as such

`M = z*\sigma = 1.96*16 = 31.36`

The lower end of the interval is the mean subtracted by M. So it is 315 - 31.36 = 283.64 watts.

The upper end of the interval is the mean added to M. So it is 6315 + 31.36 = 346.36 watts.

The 95% confidence interval for the mean peak power after training is (283.64 watts, 346.34 watts).