a. Find the least square estimates of the unknown parameters a and 3. Provide a 95% confidence interval for 3. Interpret your interval estimate. b. Test whether or not there is a linear association between the hardness of the plastic and the elapsed time at the 5 percent significance level. State the null and alternative hypotheses, decision rule, P-value of the test, and conclusion. c. Obtain the Type II error of your test in part (b) if HA B = 2.5. Assume Var(b)=0.008. d. Obtain a 95 percent confidence interval for the mean hardness of molded items with an elapsed time of 30 hours. Interpret your confidence interval. e. Obtain a 95 percent prediction interval for the mean hardness of 10 newly molded test items, each with an elapsed time of 30 hours.

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Sixteen batches of the plastic were made, and from each batch one test item was
molded. Each test item was randomly assigned to one of the four predetermined time
levels, and the hardness was measured after the assigned elapsed time. The results
are shown below; X is the elapsed time in hours, and Y is hardness in Brinell units.
Assume the following regression model
Y₁ = a + BX₁ + ₁, i = 1,..., 10
iid
where a and 3 are unknown constants and e
N(0, 2), o> 0 holds true.
i
1 2 3 4 5
X₁ 16 16 16 16 24
Y₁ 199 205 196 200 218
where Σ=1i
Ei=103656.
8
6 7
9 10 11 12
24 24 24 32 32 32 32
220 215 223 237 234 235
230
= 448, 1yi 3609, Στ
=
13824, Σ
=
13 14 15 16
40 40 40 40
250 248 253 246
819499, and
Transcribed Image Text:Sixteen batches of the plastic were made, and from each batch one test item was molded. Each test item was randomly assigned to one of the four predetermined time levels, and the hardness was measured after the assigned elapsed time. The results are shown below; X is the elapsed time in hours, and Y is hardness in Brinell units. Assume the following regression model Y₁ = a + BX₁ + ₁, i = 1,..., 10 iid where a and 3 are unknown constants and e N(0, 2), o> 0 holds true. i 1 2 3 4 5 X₁ 16 16 16 16 24 Y₁ 199 205 196 200 218 where Σ=1i Ei=103656. 8 6 7 9 10 11 12 24 24 24 32 32 32 32 220 215 223 237 234 235 230 = 448, 1yi 3609, Στ = 13824, Σ = 13 14 15 16 40 40 40 40 250 248 253 246 819499, and
a. Find the least square estimates of the unknown parameters a and ß. Provide a
95% confidence interval for 3. Interpret your interval estimate.
b. Test whether or not there is a linear association between the hardness of the
plastic and the elapsed time at the 5 percent significance level. State the null and
alternative hypotheses, decision rule, P-value of the test, and conclusion.
:
c. Obtain the Type II error of your test in part (b) if HA 3 = 2.5. Assume
Var(b) = 0.008.
d. Obtain a 95 percent confidence interval for the mean hardness of molded items
with an elapsed time of 30 hours. Interpret your confidence interval.
e. Obtain a 95 percent prediction interval for the mean hardness of 10 newly molded
test items, each with an elapsed time of 30 hours.
Transcribed Image Text:a. Find the least square estimates of the unknown parameters a and ß. Provide a 95% confidence interval for 3. Interpret your interval estimate. b. Test whether or not there is a linear association between the hardness of the plastic and the elapsed time at the 5 percent significance level. State the null and alternative hypotheses, decision rule, P-value of the test, and conclusion. : c. Obtain the Type II error of your test in part (b) if HA 3 = 2.5. Assume Var(b) = 0.008. d. Obtain a 95 percent confidence interval for the mean hardness of molded items with an elapsed time of 30 hours. Interpret your confidence interval. e. Obtain a 95 percent prediction interval for the mean hardness of 10 newly molded test items, each with an elapsed time of 30 hours.
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