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Laabri

APS24-2 Differences in Means

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Last updated about 5 years ago
12 Nsɛmmisa
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Watch the video below to see how to check the nearly normal condition with your calculator and do all the "mechanics" for a 2-sample t-test and a 2-sample t-interval.

Watch this video for a rather sloppy and half-hearted explanation of the 2-sample t-test and 2-sample t-interval.

Asemmisa {{asɛmmisaAhyɛnsode}}
1.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

What is the parameter and its definition?

Asemmisa {{asɛmmisaAhyɛnsode}}
2.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Is there evidence of a difference in mean pulse rates between smokers and nonsmokers? What Hypotheses would you test?

Let group 1 be smokers and group 2 be nonsmokers.

Asemmisa {{asɛmmisaAhyɛnsode}}
3.

What conditions must be checked for a 2-sample t-test?

Asemmisa {{asɛmmisaAhyɛnsode}}
4.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Is there evidence of a difference in mean pulse rates between smokers and nonsmokers?

What procedure will we complete?

Asemmisa {{asɛmmisaAhyɛnsode}}
5.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Is there evidence of a difference in mean pulse rates between smokers and nonsmokers?

Use your calculator to run a 2-sample t-test. What is the value of the t-statistic? (round to three decimals)

Asemmisa {{asɛmmisaAhyɛnsode}}
6.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Is there evidence of a difference in mean pulse rates between smokers and nonsmokers?

Use your calculator to run a 2-sample t-test. What is the p-value? (round to five decimals)

Asemmisa {{asɛmmisaAhyɛnsode}}
7.

Based on the p-value, we should

Asemmisa {{asɛmmisaAhyɛnsode}}
8.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Estimate the difference in the true mean pulse rates for smokers and nonsmokers.

What procedure will we complete?

Asemmisa {{asɛmmisaAhyɛnsode}}
9.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Create a 95% confidence interval to estimate the true difference in mean pulse rates. (round each part to three decimals)

Asemmisa {{asɛmmisaAhyɛnsode}}
10.

Resting pulse rates for a random sample of 26 smokers had a mean of 80 beats per minute (bpm) and a standard deviation of 5 bpm. Among 32 randomly chosen nonsmokers, the mean and standard deviation were 74 and 6 bpm. Both sets of data were roughly symmetric and had no outliers.

Conclude your confidence interval from number 9.

Asemmisa {{asɛmmisaAhyɛnsode}}
11.

If we want our results for our interval (95% confidence) and hypothesis test (2-sided alternative) to be consistent, what alpha level should we use for our hypothesis test?

Asemmisa {{asɛmmisaAhyɛnsode}}
12.

Here are the saturated fat content (in grams) for several pizzas sold by two national chains. Is there a significant difference in the fat content of the brands? How big is the difference? Be sure that in checking the conditions, you plot both sets of data.

Complete a full hypothesis test. I'd recommend doing it on paper, taking a picture, and putting it on the "show your work" board.