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Growth hormones are often used to increase the weight gain of chickens. In an experiment using 15chickens, five different doses of growth hormone (0, 0.2, 0.4, 0.8, and 1.0milligrams) were injected into chickens (3chickens were randomly assigned to each dose), and the subsequent weight gain (in ounces) was recorded. A researcher plots the data and finds that a linear relationship appears to hold. Computer output from a least-squares regression analysis for these data is shown below.

role="math" localid="1652870715985" PredictorCoefSE CoefTPConstant4.54590.61667.37<0.0001Dose4.83231.01644.750.0004S=3.135R-Sq=38.4%R-Sq(adj)=37.7%

(a) What is the equation of the least-squares regression line for these data? Define any variables you use.

(b) Interpret each of the following in context:

(i) The slope

(ii) The yintercept

(iii) s

(iv) The standard error of the slope

(v) r2

(c) Assume that the conditions for performing inference about the slope B of the true regression line are met. Do the data provide convincing evidence of a linear relationship between dose and weight gain? Carry out a significance test at the A =0.05level.

(d) Construct and interpret a 95%confidence interval for the slope parameter.

Short Answer

Expert verified

(a) The equation of the least-squares regression line isy^=4.5459+4.8323x.

(b) The values are

(i) b=4

(ii) a=4.5450

(iii) s=3.135

(iv) SEb=1.0164

(v)role="math" localid="1652871593895" r2=38.4%

(c) There's sufficient convincing evidence to justify the argument.

(d) There is a 95%chance that the weight gain will be between 2.636876and 7.027724. While the does, the ounces climb by 1milligram.

Step by step solution

01

Part(a) Step 1: Given Information

PredictorCoefSE CoefTPConstant4.54590.61667.37<0.0001Dose4.83231.01644.750.0004S=3.135R-Sq=38.4%R-Sq(adj)=37.7%

02

Part(a) Step 2: Explanation

a=4.5459

b=4.8323

The general regression line equation

y^=a+bx

By inserting values the regression line becomes:

role="math" localid="1652870965008" y^=4.5459+4.8323x

With xDose and yweight gain.

03

Part(b) Step 1: Given Information

PredictorCoefSE CoefTPConstant4.54590.61667.37<0.0001Dose4.83231.01644.750.0004S=3.135R-Sq=38.4%R-Sq(adj)=37.7%

04

Part(b) Step 2: Explanation

(i) b=4is the first output. The weight per milligram might increase by 4.8323ounces.

(ii). In the result a=4.5450, the y-intercept is mentioned.

This means that the weight will be 4.5459ounces if the dosage is 0milligrams.

(iii) s=3.135is the output. This means that the average prediction error is 3.1350ounces.

(iv) SEb=1.0164This suggests that the population's true slope is 1.016-1on average over all feasible samples.

(v)r2is written asr2=R-Sq=38.4%. This means that the least-square regression line explains 38.4%of the variance in the variables.

05

Part(c) Step 1: Given Information

PredictorCoefSE CoefTPConstant4.54590.61667.37<0.0001Dose4.83231.01644.750.0004S=3.135R-Sq=38.4%R-Sq(adj)=37.7%

06

Part(c) Step 2: Explanation

Define hypothesis

H0:=0

H1:0

The test statistic is

t=b-0SEb=4.8323-01.0164=4.754

The P-value is the probability of having the test numbers' value or a more dramatic value. The t-value in the rowrole="math" localid="1652872078633" df=n-2=15-2=13 is represented by a number (or interval) in Table B column title:

P<0.0005

The null hypothesis is rejected if the p-value is less than or equal to the degree of significance.

P<0.05RejectH0

07

Part(d) Step 1: Given Information

PredictorCoefSE CoefTPConstant4.54590.61667.37<0.0001Dose4.83231.01644.750.0004S=3.135R-Sq=38.4%R-Sq(adj)=37.7%

08

Part(d) Step 2: Explanation

Degrees of freedom

df=n-2=15-2=13

Table B, in the row of df=13and the column of c=95%, has the important t-value.

The essential t-value may be found in table B in the c=95%column and in the df=13row.

t*=2.160

The boundaries are

role="math" localid="1652872255479" b-t*SEb=4.8323-2.1601.0164=2.636876

b+t*SEb=4.8323+2.1601.0164=7.027724

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