00:01
An agricultural researcher plants 25 plots with new varieties of corn.
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The average yield for these plots is 150 bushels per acre.
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So we have a sample size of 25.
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We have a sample mean of 150.
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Assume that the yield per acre for the new variety of corn follows a normal distribution with unknown mean and a standard deviation of 10 bushels.
00:30
The 90 % confidence interval would be, so we're going to find that.
00:40
And then we're going to play around a little bit with our numbers.
00:46
So let's just start with a 90 % confidence interval.
00:50
So we're going to take 150 plus or minus.
00:53
Since we know the standard deviation, we can go ahead and use critical value from z, and then we'll take 10 divided by the square root of 25.
01:05
So our 90 % confidence interval, we have 150 plus or minus 3 .29.
01:11
Which gives us an interval of 146 .71 to 153 .29...