00:01
Let me take note the given information here, the sample size which is given as 25 here, and the sample mean which is denoted by x bar that was given as 70 inches, and the sample standard division which is denoted by s that was given as 10 here, and the confidence level which is given as 90 percent so we can write that 0 .90.
00:19
What we're going to find? we're going to find the confidence interval for the population mean.
00:23
Let's remember this formula, the confidence interval for the population mean which is sample mean plus or minus.
00:29
Because we know the sample standard division we have to use the t distribution at this step which is t alpha over 2 sample standard division divided by root n.
00:38
So the alpha is 1 minus confidence level but we need alpha over 2 which means this is 1 minus 0 .90 divided by 2 which would be 0 .05 and also we need the degrees of freedom n minus 1.
00:50
This is 25 minus 1 which is 24.
00:53
To get the t value here i'm going to use the inverse t function for the graphing display calculator.
00:59
So the area was 0 .05 and the degrees of freedom is 24.
01:03
Press second, variance, and the inverse t this is 0 .05 and then the degrees of freedom is 24...