00:01
Hello, so here we're given the sample size n is 50.
00:04
The sample mean x bar is 19 .4, and the population standard deviation sigma is equal to 2.
00:10
So here we have our hypotheses, h -0, is that mu is greater than equal to 20, and our alternative hypothesis is that mu is less than 20.
00:18
So then the test statistic for the hypothesis test about a population mean, when sigma is known, is given by z is equal to x bar minus mu, u -n -n divided by sigma divided by a square of n, that's going to equal to 19 .4 minus 20 divided by 2 divided by a square root of 50, which is going to be equal to about negative 2 .12.
00:47
And then for part b, we have that the area under the standard normal curve to the left of z equals negative 2 .12 is obtained from our table, and we get the probability here of z being less than or equal.
01:02
To negative 2 .12 is going to be equal to 0 .017.
01:07
So the p value for this left tail test is p equal to 0 .017.
01:13
And then for part c, we've given that alpha is 0 .05...