00:01
For this exercise, we are given two intervals, confidence intervals.
00:05
Apparently, both are confidence intervals for the true mean of the resonance frequency for all tennis rackets of a certain type.
00:15
And for part a, we are asked, what is the sample average that was used to create these confidence intervals? what was the sample mean resonance frequency? now, when we have a confidence interval on a population mean, it is constructed by using the sample.
00:37
Average as the midpoint of the interval.
00:39
So all we have to do here is find the midpoint of these intervals.
00:45
And that is just the average of the two ends of the interval.
01:00
And this comes out to 115.
01:03
And if you do that with the other confidence interval, you get the same result.
01:08
So we know that the sample average used to construct these confidence intervals was 115 hertz.
01:17
Next for part b, we are told that both intervals were calculated from the same sample data.
01:21
The difference is one is a 90 % interval and the other is a 99 % interval...