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T12.11 Growth hormones are often used to increase the weight gain of chickens. In an experiment using 15 chickens, 3 chickens were randomly assigned to each of 5 different doses of growth hormone (0, 0.2, 0.4, 0.8, and 1.0 milligrams). The subsequent weight gain (in ounces) was recorded for each chicken. A researcher plots the data and finds that a linear relationship appears to hold. Here is computer output from a least-squares
regression analysis of these data. Assume that the conditions for performing inference about the slope 1of the true regression line are met.

a. Interpret each of the following in context:
i. The slope
ii. The y intercept
iii. The standard deviation of the residuals
iv. The standard error of the slope
b. Do the data provide convincing evidence of a linear relationship between dose and weight gain? Carry out a significance test at the =0.05 level.
c. Construct and interpret a 95%confidence interval for the slope parameter

Short Answer

Expert verified

(a)(i) The slope is 4.8323.

(ii) The y intercept is 4.5459.

(iii) The standard deviation of the residuals is SEb1=1.0164.

(iv) The standard error of the slope is 1.0164.

(b) There is a sufficient evidence to support the claim.

(c) The dose is increased by one milligrams, the weight gain increases between 2.636876and 7.027724ounces at 95%confidence interval.

Step by step solution

01

Part (a) Step 1: Given information

To interpret the slope, the y intercept, the standard deviation of the residuals ans the standard error of the slope.

02

Part (a) Step 2: Explanation

To increase the weight of the chicken, growth hormones are applied. As a result, the experiment was carried out, and the weight gain was recorded. When a researcher plots the data, notices that it looks to be linear relationship. The question includes a computer output assuming that the prerequisites for making inferences about the slope of the regression line are met. As a result,
(i) The slope: The slope b1 of the supplied computer output is presented in the row "Dose" and the column "Coef," i.e.,
b1=4.8323
The slope shows how much y has increased or decreased per unit of x.
Weight gain increases by 4.8323 ounces per mg of growth hormone on average.
(ii) In the row "Constant" and the column "Coef" of the given computer output, the y-intercept of b0 is presented as,
b0=4.5459
When xis zero, the y-intercept indicates the average y-value.
When the growth hormone dose is 0mg, the weight gain is localid="1654258733317" 4.5459ounces on average.

(iii) The standard error of the estimate s is presented as:
s=3.135
The standard error of predictions, or the average difference between actual y-values and expected y-values, is represented by the standard error of the estimate s. As a result, the expected weight gain differs by 3.135 ounces on average from the actual weight gain.
In the row "Dose" and the column "SE Coef" of the given computer output, the standard error of the slope SEb1 is presented as:
localid="1654258767678" SEb1=1.0164.
(iv) The standard error of the slope indicates the mean deviation of the slope of the sample regression line from the slope of the population regression line. As a result, the slope of the sample regression line differs from the true population regression line by an average of 1.0164.

03

Part (b) Step 1: Given information

To determine the data provide convincing evidence of a linear relationship between dose and weight gain at a significance test =0.05 level.

04

Part (b) Step 2: Explanation

To increase the weight of the chicken, growth hormones are applied.
As a result, the experiment was carried out, and the weight gain was recorded. When a researcher plots the data, notices that it looks to be linear relationship. The question includes a computer output assuming that the prerequisites for making inferences about the slope of the regression line are met. As a result,
b=4.8323
SEb=1.0164
n=15
The hypotheses are now specified as follows:
H0:=0
H1:0
The value of test statistics is determined as follows:
t=b-0SEb
=4.833-01.0164
4.754

Determine the degrees of freedom is determined as follows:
df=n-2
=15-2
=13
Since, the P-value is the probability of getting the test statistic's value or a number that is more severe.
As a result, the P-value is as follows:
P<0.0005
The null hypothesis is rejected if the P-value is less than or equal to the significance level.
Accordingly,
P<0.05RejectH0
As a result, there is a sufficient evidence to support the claim.

05

Part (c) Step 1: Given information

To construct and interpret a 95% confidence interval for the slope parameter.

06

Part (c) Step 2: Explanation

To increase the weight of the chicken, growth hormones are applied.
As a result, the experiment was carried out, and the weight gain was recorded. When a researcher plots the data, notices that it looks to be linear relationship. The question includes a computer output assuming that the prerequisites for making inferences about the slope of the regression line are met. As a result,

b=4.8323
SEb=1.0164
n=15
Determine the degrees of freedom as follows:
df=n-2
=15-2
=13
In the table B, the crucial value may be found in the row of df=13and the column of c=95%, such that
t*=2.160
Determine the confidence interval as follows:
b-t*SEb
=4.8323-2.1601.0164
=2.636876
b+t*SEb
=4.8323+2.1601.0164
=7.027724
As a result, conclude that 95%confidence the dose is increased by one milligrams, the weight gain increases between 2.636876and 7.027724ounces.

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