00:01
Once again, welcome to a new problem.
00:04
This time we're dealing with confidence interval.
00:10
We're dealing with confidence interval.
00:13
And when it comes to confidence interval, we have confidence interval for means, and the formula for confidence interval for means is x bar.
00:23
Tr for over 2 with the degrees of freedom, n minus 1, s over radical n.
00:32
And we could also have confidence interval for variance.
00:38
And so for variance, we have specific requirements for the confidence interval.
00:45
This time we have the kai square critical value.
01:02
And so we have a new problem.
01:04
And in this particular problem, we have a sample size of 20 students.
01:10
And these students are randomly selected, and the required measurement is stimulus reaction times.
01:27
And these reaction times have normal distribution, and just so happens that the mean of this distribution is 0 .9 seconds, and the standard deviation for this distribution is 0 .12 seconds.
01:46
We want to determine the confidence interval, 95 % confidence interval of the unknown population means.
02:02
So we're looking for 95 % confidence interval.
02:05
So we're going to do x bar t -r -4 over 2, s of a radical n.
02:11
Remember degrees of freedom is 20 minus 1, which is 19.
02:15
And so we have 0 .9 plus minus t alpha over 2 is 2 .093.
02:23
The standard deviation is 0 .12 all over radical n is radical 20.
02:30
And that allows us to get the confidence interval this time, which is equivalent to 0 .84, 384, up until 0 .0 .84, up until 0 .0 .0.
02:50
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