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Thank you We sneak and here's your shmoop du jour

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brought to you by fancy pants canines They desire the

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finer things in life and it's a pity they have

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to settle for us Here's the question A simple random

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sample of three hundred poodles is taken from a population

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of two thousand poodles in the samples The average number

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of fancy pants canine biscuits eaten per day was three

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point eight with a standard deviation of one point one

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What is the ninety nine percent confidence interval for the

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dog's biscuit consumption And here the possible answers All right

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three point eight plus or minus what Okay well let's

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walk through this and be sure to keep muttering to

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yourself that there's nothing you'd rather be doing at this

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moment than working with statistical inference muttering that makes it

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harder to screen All right we need a confidence interval

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for a mean so we need to know if the

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sample is a simple random sample With means yes but

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we don't think dogs even know how to say no

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No way Okay next Is the population normally distributed with

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a sample size of thirty or more Yeah Sample sizes

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three hundred so slightly bigger than thirty How about the

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standard deviation P no dice It wasn't given and we

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have no way of calculating it So we'll calculate the

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confidence interval like this sample estimate plus or minus critical

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value times standard deviation of the estimate Since we were

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never given p which is still a sore spot for

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us we must use tea instead of ze since p

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is unknown So our equation looks like this This ugly

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thing right there the calculate t look at the t

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distribution table that's the chart with all the columns and

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all the numbers Once your eyes adjust focus on the

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column with the ninety nine percent of the bottom There

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are three hundred minus one degrees of freedom otherwise known

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as two hundred ninety nine Since the table doesn't give

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us two ninety nine we have to use the closest

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number below two ninety nine which is one hundred So

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the info that we've gathered calculated and otherwise bemoan gives

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us t equals two point six two six which we

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can plug into our equation and we get three point

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eight plus or minus zero point one six seven And

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what do you know that looks familiar Answer D is

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the correct choice And hey if you want to impress

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your fancy pants canine try explaining statistical inference to him

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So they probably already learned it during their time at 00:02:23.84 --> [endTime] harvard

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