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Thank you We sneak and here's your smoke too Sure

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brought to you by distraction It's usually not a good

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thing but sometimes who Look a squirrel All right way

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surveyed a simple random sample of twenty eights world to

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find the average number of nuts collected before winter to

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calculate and ninety eight percent confidence interval for the average

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number of nuts collected We should do which of the

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following and here the financial answers Okay so what's a

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ninety eight percent confidence interval in statistics A confidence interval

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is an interval or range of likely population values from

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which we might obtain our estimate of the average In

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this case the average number of nuts collected Yeah a

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ninety eight percent confidence interval refers to a range in

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which we're ninety eight percent sure that the true mean

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or average lives within those numbers Okay so first of

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all we're calculating a confidence interval for means or averages

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not proportions So we have to be nuts to eat

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Picking a glance of a three day we noticed that

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we should be solving for either the tea or than

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see critical value which first of this year team distributions

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when do we use the sea And when do we

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use t Well it's actually requires us to know something

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called the central limit Mira it tells us that the

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sampling distribution of a sample means is approximately normal When

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the sample size is large enough like say more than

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thirty If our sample size is large enough we can

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use c procedures to analyze samples If not we have

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to use t procedure Okay in this case our sample

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size is not large enough so we have to use

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t procedures which leaves us with your b or c

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is the answer all right A little bit about the

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team distribution The tea distribution changes based on sample size

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and is determined by the number of degrees of freedom

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which is basically just the sample size and minus one

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closer end is two Thirty the more it looks normal

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like ze distribution with our sample size of twenty eight

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squirrels the degrees of freedom or df is twenty eight

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minus one or twenty seven We're looking for a ninety

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eight percent confidence level So if we shade in the

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middle of the distribution is ninety eight percent We're left

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With two talents of one percent or point o one

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though the tea distribution table which is provided in every

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stats test shows us that thi equals two point four

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seven three for ninety eight percent Confidence level and bf

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equals twenty seven And today our answer is c

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