00:02
First we have to set up hypothesis.
00:05
So null hypothesis, the mean life of the new brand of bulbs is not greater than 900 hours.
00:31
So mean is less than equal to 900.
00:35
Then alternative hypothesis, the mean life of the new brand of bulbs is greater than 900 hours.
01:02
So mean is greater than 900.
01:06
Now, secondly, we have to choose the significance level.
01:10
So the significance level is given as 10 % which means alpha is equal to 0 .10.
01:26
Then we have to calculate these test statistics.
01:29
So given information, sample mean is equal to 920 hours, population standard deviation is equal to 80 hours and sample size is equal to 64.
01:47
So the test hypothesis, the test statistic for one sample z test is calculated as z is equal to sample mean subtracted from mean divided by standard deviation divided by root n.
02:00
Now, we will substitute the values which is equal to 920 subtracted from 900 divided by 80 divided by root 64, which is equal to 20 divided by 10 evaluating it.
02:12
We get 2.
02:14
Then we have to determine the critical value...