Inference for a Population Mean Review. How do sample means vary? According to a bell curve The...
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Transcript of Inference for a Population Mean Review. How do sample means vary? According to a bell curve The...
Inference for a Population Mean
Review
How do sample means vary?
• According to a bell curve
• The average of the sample means is the population mean
• The standard deviation is the population standard deviation divided by the square root of the sample size.
Two types of inference
• Confidence Interval – Used to estimate a population mean.
• Hypothesis test – Used to test a claim about the population mean.
Confidence Interval Formula to Estimate a Population Mean
• If the population standard deviation is known or the sample size is large:
• If the population standard deviation is not known and the sample size is less than 30
nzx
*
_
n
stx *
_
Hypothesis Test to Test a Population Mean
• Null Hypothesis:
• Collect a random sample and compute a sample mean and standard deviation.
• Compute the t-test statistic
• Find the p-value
• State your conclusions.
00 : H
Looking Ahead
• Is there any association between gender and the amount of time one exercises per week?
• Is there any association between the model of SUV’s and highway gas mileage?
Correlation
• Both examples involve investigating correlation between a CATEGORICAL and a NUMERIC variable.
• Recall the appropriate test in this situation is ANOVA.
Section 7.3
• Understanding the Difference Between Sample Variability and Within Sample Variability
• We’ll use an example involving highway m.p.g. of various models of trucks to motivate this topic.