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Does how long young children remain at the lunch table help predict how much they eat? Here are data on a random sample of 20toddlers observed over several months. 鈥淭ime鈥 is the average number of minutes a child spent at the table when lunch was served. 鈥淐alories鈥 is the average number of calories the child consumed during lunch, calculated from careful observation of what the child ate each day.


Here is some computer output from a least-squares regression analysis of these data. Do these data provide convincing evidence at the =0.01=0.01level of a linear relationship between time at the table and calories consumed in the population of toddlers?


PredictorCoefSECoefTPConstant560.6529.3719.090.000Time3.07710.84983.620.002S=23.3980R-Sq=42.1%R-Sq(adj)=38.9%

Short Answer

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Step by step solution

01

Given Information

We need to

02

Simplify

Consider:

n=Samplesize=20=Significancelevel=0.01

The estimate of the slope b1is given in the row "Time" and in the column "Coef" of the given computer output:

b1=-3.0771

The estimated standard deviation of the slope role="math" localid="1654164770191" SEb1is given in the row "Time" and in the column "SE Coef" of the given computer output:

SEb1=0.8498

Given claim: Slope is nonzero:

The null hypothesis or the alternative hypothesis states the given claim The null hypothesis states that the slope is zero. If the given claim is the null hypothesis, then the alternative hypothesis states the opposite of the null hypothesis.

H0:1=0H:10

Compute the value of the test statistic:

t=b11SEb1=3.077100.8498-3.6210

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the Student's T table in the appendix containing the -value in the row df=n2=202=18We can ignore the minus sign in the test statistic:

0.001=2(0.0005)<P<2(0.001)=0.002

If the P-value is less than or equal to the significance level, then the null hypothesis is rejected:
P<0.01RejectH0

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Most popular questions from this chapter

Prey attracts predators Here is one way in which nature regulates the size of animal populations: high population density attracts predators, which remove a higher proportion of the population than when the density of the prey is low. One study looked at kelp perch and their common predator, the kelp bass. On each of four occasions, the researcher set up four large circular pens on sandy ocean bottoms off the coast of southern California. He randomly assigned young perch to 1of 4pens so that one pen had 10perch, one pen had 20perch, one pen had 40perch, and the final pen had 60perch. Then he dropped the nets protecting the pens, allowing bass to swarm in, and counted the number of perch killed after two hours. A regression analysis was performed on the16 data points using x=number of perch in pen and y=proportion of perch killed. Here is a residual plot and a histogram of the residuals. Check whether the conditions for performing inference about the regression model are met.


Here is computer output from the least-squares regression analysis of the perch data.

a. Find the critical value for a 90%confidence interval for the slope of the true regression line. Then calculate the confidence interval.

b. Interpret the interval from part (a).

c. Explain the meaning of 鈥90% confident鈥 in this context.

An experimenter wishes to test if one of two types of fish food (a standard fish food and a new product) is better for producing fish of equal weight after a two-month feeding program. The experimenter has two identical fish tanks (1 and 2) and is considering how to assign 40 fish, each of which has a numbered tag, to the tanks. The best way to do this would be to

a. put all the odd-numbered fish in Tank 1 and the even-numbered fish in Tank 2. Give the standard food to Tank 1 and the new product to Tank 2.

b. obtain pairs of fish whose weights are roughly equal at the start of the experiment and randomly assign one of the pair to Tank 1 and the other to Tank 2. Give the standard food to Tank 1 and the new product to Tank 2.

c. proceed as in option (b), but put the heavier of each pair into Tank 2. Give the standard food to Tank 1 and the new product to Tank 2.

d. assign the fish completely at random to the two tanks using a coin flip: heads means Tank 1 and tails means Tank 2. Give the standard food to Tank 1 and the new product to Tank 2.

e. divide the 40 fish into two groups, with the 20 heaviest fish in one group. Randomly choose which tank to assign the heaviest fish and assign the lightest fish to the other tank. Give the standard food to Tank 1 and the new product to Tank 2.

The school board in a certain school district obtained a random sample of 200residents and asked if they were in favor of raising property taxes to fund the hiring of more statistics teachers. The resulting confidence interval for the true proportion of residents in favor of raising taxes was (0.183,0.257). Which of the following is the margin of error for this confidence interval?

a. 0.037

b. 0.074

c. 0.183

d. 0.220

e.0.257

Multiple Choice Select the best answer for Exercises 23-28. Exercises 23-28 refer to the following setting. To see if students with longer feet tend to be taller, a random sample of 25students was selected from a large high school. For each student, x=footlengthand y=heightwere recorded. We checked that the conditions for inference about the slope of the population regression line are met. Here is a portion of the computer output from a least-squares regression analysis using these data:

Is there convincing evidence that height increases as footlength increases? to answer this question, test the hypothesis

a.H0:1=0H0:1=0versusH:1&gt;0.H:1>0

b.H0:1=0H0:1=0versusH:1<H:1&lt;0

cH0:1=0H0:1=0versusH:10.H:10

dH0:1&gt;0H0:1>0versusH:1=0.H:1=0

e.H0:1=0H0:1=0versusH:1&gt;1.H:1>1

In a recent poll, randomly selected New York State residents at various fast-food restaurants were asked if they supported or opposed a "fat tax" on sugared soda. Thirtyone percent said that they were in favor of such a tax and 66% were opposed. But when asked if they would support such a tax if the money raised were used to fund health care given the high incidence of obesity in the United States, 48% said that they were in favor and 49% were opposed.
(a) In this situation, explain how bias may have been introduced based on the way the questions were worded and suggest a way that the questions could have been worded differently in order to avoid this bias.
(b) In this situation, explain how bias may have been introduced based on the way the sample was taken and suggest a way that the sample could have been obtained in order to avoid this bias.
(c) This poll was conducted only in New York State. Suppose the pollsters wanted to ensure that estimates for the proportion of people who would support a tax on sugared soda were available for each state as well as an overall estimate for the nation as a whole. Identify a sampling method that would achieve this goal and briefly describe how the sample would be taken.

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