Chapter 13 Notes

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Comparing Two Means:

Conditions:

Z-Statistic:

Do you ever use a z-statistic?

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t-test statistic and standard error:

Confidence Interval:

Hypothesis:

Degrees of Freedom:

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2-Proportion Z test:

Standard Deviation:

Confidence Interval:

Test Statistic:

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Practice Problems:

A study of adverse symptoms in users of over the counter pain relief medications assigned subjects at random to one of two pain relievers A & B. 650 took A and 44 experienced adverse symptoms. 347 took B and 49 had adverse symptoms. Is there evidence that the two pain relievers differ in proportion of adverse symptoms. Preform the appropriate test and construct a 90% confidence interval.

In a study of heart surgery

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1. Baby walkers are

seats hanging from frames that allow babies to sit upright with their legs

dangling and feet touching the floor.

Walkers have wheels on their legs that allow the infant to propel the

walker around the house long before he or she can walk or even crawl. Typically, babies use walkers between the

ages of 4 months and 11 months.

Because most walkers have tray tables in

front that block babies’ views of their feet, child psychologists have begun to

question whether walkers affect infants’ cognitive development. One study compared mental skills of a random

sample of those who used walkers with a random sample of those who never used

walkers. Mental skill scores averaged

113 for 54 babies who used walkers (standard deviation of 12) and 123 for 55

babies who did not use walkers (standard deviation of 15). Use the appropriate test and construct a 99% confidence interval

n1: 605 n2:195 y1:351 y2:41

Time magazine reported the result of a telephone poll of 800 adult Americans. The question posed of the Americans who were surveyed was: "Should the federal tax on cigarettes be raised to pay for health care reform?" The results of the survey were:

Is there sufficient evidence at the α = 0.05 level, say, to conclude that the two populations — smokers and non-smokers — differ significantly with respect to their opinions?