# AP Statistics 1.4 Statistical Inference

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AP Statistics 1.4 Statistical Inference. What is the 99% confidence interval for the dogs' biscuit consumption?

AP Statistics | Statistical Inference |

Anticipating Patterns | Sampling Distributions |

Language | English Language |

Sampling And Experimentation | Planning and Conducting Experiments |

### Transcript

of two thousand poodles in the samples The average number

of fancy pants canine biscuits eaten per day was three

point eight with a standard deviation of one point one

What is the ninety nine percent confidence interval for the

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

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

walk through this and be sure to keep muttering to

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

moment than working with statistical inference muttering that makes it

harder to screen All right we need a confidence interval

for a mean so we need to know if the

sample is a simple random sample With means yes but

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

No way Okay next Is the population normally distributed with

a sample size of thirty or more Yeah Sample sizes

three hundred so slightly bigger than thirty How about the

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

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

confidence interval like this sample estimate plus or minus critical

value times standard deviation of the estimate Since we were

never given p which is still a sore spot for

us we must use tea instead of ze since p

is unknown So our equation looks like this This ugly

thing right there the calculate t look at the t

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

all the numbers Once your eyes adjust focus on the

column with the ninety nine percent of the bottom There

are three hundred minus one degrees of freedom otherwise known

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

us two ninety nine we have to use the closest

number below two ninety nine which is one hundred So

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

us t equals two point six two six which we

can plug into our equation and we get three point

eight plus or minus zero point one six seven And

what do you know that looks familiar Answer D is

the correct choice And hey if you want to impress

your fancy pants canine try explaining statistical inference to him

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