00:02
Okay, so i've written the question down here, so our sample size is 85 employees, the mean is 4 .5 days, and the standard deviation is 1 .2 days.
00:13
And we're looking to make confidence intervals at 95 and 92%.
00:18
On the right is the standard normal distribution table, what you'll need to answer this question.
00:24
So i'm going to start off by writing on the equation that you need to get the confidence intervals, and then i'll explain what it means.
00:30
So to get the confidence intervals, this is the equation.
00:43
And so the mean standard deviation in the sample size is all defined.
00:48
The z score at alpha over 2 you'll get from the table.
00:52
And alpha is equal to 1 minus your confidence level.
00:56
And your confidence level will be 95 % or 92%.
01:00
So let's begin with the 95%.
01:06
Your alpha will equal 1 minus your confidence.
01:10
0 .95 because it's in a percentage and that'll be 0 .05 and we want alpha 2 which will equal 0 .025.
01:23
So then you come over to the normal distribution table and you look for 0 .25 or 0 .025 sorry.
01:33
Then you see that it's at negative 1 .96 and that is your z score.
01:41
So see a z alpha over 2 is equal to negative 1 .96.
01:48
So what this means is that on your standard distribution table, that was really bad.
01:56
All right.
01:57
So your standard distribution table between here, this is your 95%.
02:04
And the remainder is 0 .05, but we're dividing that in half.
02:13
So this would be 0 .025.
02:16
This would be 0 .025.
02:20
And you always look to see what's left of the z score.
02:23
So you'll have negative 1 .96 here...