How many colleges did you apply to?. Type the number into your clicker and hit “send”. 10-2 Estimating a Population Mean (σ Unknown). Confidence Intervals in the Calculator.
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Estimating a Population Mean
Using the Calculator
In other words… the standard error is (most likely) an inaccurate estimate of a (population) standard deviation.
We call it the t distribution.The t distributions
We specify a t distribution by giving its degrees of freedom, which is equal to n-1
We will write the t distribution with k degrees of freedom as t(k) for short.
We also will refer to the standard Normal distribution as the z-distribution.
Compare the shape, center, and spread of the t-distribution with the z-distribution.
As the degrees of freedom k increase, (the sample size increases), the t-distribution is increasingly Normal.
- n < 15 : Use t procedures if data are close to Normal with no outliers
- n ≥ 15 : Use t procedures except in cases of outliers of strong skew
- n ≥ 30 : Use t-procedures even for clearly skewed distributions (cannot have extreme outliers)
Given Study Tool
No Study Tool
Study– No Study
250, 280, 220, 280, 320
Find the sample mean and sample standard deviation
Construct a 90% confidence interval on the average monthly demand per outlet.