00:01
So a question says that the quality control department of a wire manufacturing periodically select a sample of wire specimen in order to test for the breaking strength.
00:09
Past experience has shown that the breaking strength of the certain type of wires are normally distributed with a standard deviation of 200 kg.
00:17
A random sample of 64 specimens gave a mean of 6 ,200 kg.
00:22
So let's go to our worksheet.
00:24
We have our population standard divisions because to 200 kg.
00:28
We have our sample size earned to be cost to 64 and we have our sample to be cost to 6 ,200 kg.
00:36
So the question says that determining 95 % confidence in time for the main breaking strength of the population to suggest to the quality control supervisor.
00:46
Our confidence level better is 95%.
00:49
To construct a 95 % confidence in time we have a formula that says m is equals to x bar plus or minus the critical value times sigma divided by the describe rate of n so we have all of our details ready aside the critical value which is dependent on the type of distribution that defines the data set as we can see our sample size 64 is greater than 30 and our population standard division is known this simply implies that our data set is normally distributed that is our critical value is going to be is this core so our confidence level better is the cost to 95%.
01:28
That means our alpha level is going to be 5%.
01:32
So i'll be using a calculator to get my critical value...