00:01
From the given information, the level of significance, alpha is equal to 0 .05.
00:07
The sample size, n is equal to 50.
00:11
So, the degrees of freedom is equal to sample size less than 1, equal to 49.
00:18
The confidence interval formula is, confidence interval is equal to x bar plus or minus t into alpha by 2, n minus 1, into s by square root of n.
00:35
Here we consider alpha a 0 .05.
00:39
Since the population standard deviation is unknown, we can use the t confidence interval.
00:45
Now we have to calculate the sample mean and sample standard deviation.
00:51
The sample mean x bar can be calculated using excel.
00:55
In excel, type the formula equal to average a1 to a 50 and click enter.
01:07
Now we will get the sample mean.
01:10
The sample mean is 15 .40.
01:18
Now we have to identify the sample standard deviation.
01:23
In excel, type the formula equal to standard deviation stdiv.
01:30
S sample a1 to a50 and click enter.
01:37
We can identify the sample standard deviation as 4 .413...