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In an experiment to assess the effect of the angle of pull on the force required to cause separation in electrical connectors, four different angles (factor A) were used, and each of a sample of five connectors (factor B) was pulled once at each angle (鈥淎 Mixed Model Factorial Experiment in Testing Electrical Connectors,鈥 Industrial Quality Control, 1960: 12鈥16). The data appears in the accompanying table

Does the data suggest that true average separation force is affected by the angle of pull? State and test the appropriate hypotheses at level .01 by first constructing an ANOVA table (SST = 396.13, SSA = 58.16, and SSB = 246.97).

Short Answer

Expert verified

There is no significant effect due to the angle of pull at the given significance level.

Step by step solution

01

Determine the factors:

a)-

Let

Where the following holds

and where the are independent normally distributed random variable with mean 0 and varianceThe hypotheses of interest are

\({H_{0A}}:{\alpha _1} = {\alpha _2} = \ldots = {\alpha _I} = 0{\rm{\;versus\;}}{H_{aA}}:{\rm{\;at least one\;}}{\alpha _ - }i \ne 0\)

And for the factor B

\({H_{0B}}:{\beta _1} = {\beta _2} = \ldots = {\beta _J} = 0{\rm{\;versus\;}}{H_{aB}}:{\rm{\;at least one\;}}{\beta _ - }j \ne 0.{\rm{\;}}\)

With given information it is first required to construct ANOVA table and than make conclusion about appropriate hypotheses.

With given information

\(\begin{aligned}{*{20}{c}}{SST = 396.13,}\\{SSA = 58.16,}\\{SSB = 246.97,}\end{aligned}\)

it is easier to compute corresponding mean squares are the F statistic values.

02

Determine fundamental Identity:

\(SST = SSA + SSB + SSE\)

By the fundamental identity, the SSE can be computed as

\(SSE = SST - SSA - SSB = 396.13 - 58.16 - 246.97 = 91\)

When testing hypotheses H0A versus HaA, the test statistic value is

\({f_A} = \frac{{MSA}}{{MSE}},\)

and the P-value is the area under the\({F_{I - 1,(I - 1)(J - 1)}}\)curve to the right of the test statistic value fA.

When testing hypotheses\({H_{0B}}{\rm{\;versus\;}}{H_{aB}}\), the test statistic value is

\({f_B} = \frac{{MSB}}{{MSE}}\)

and the P-value is the area under the\({F_J}_{ - 1,(I - 1)(J - 1)}\)curve to the right of the test statisticvalue fB.

The degrees of freedom are

\(\begin{aligned}{*{20}{c}}{d{f_T} = IJ - 1 = 4 \cdot 5 - 1 = 19}\\{d{f_A} = I - 1 = 4 - 1 = 3}\\{d{f_B} = J - 1 = 5 - 1 = 4}\\{d{f_E} = (I - 1)(J - 1) = (4 - 1) \cdot (5 - 1) = 12}\end{aligned}\)

03

Obtain Value of test statistics:

The mean square are

\(\begin{aligned}{*{20}{c}}{MSA = \frac{1}{{I - 1}} \cdot SSA = \frac{1}{3} \cdot 58.16 = 11.4444{\rm{;\;}}}\\{MSB = \frac{1}{{J - 1}} \cdot SSB = \frac{1}{4} \cdot 246.97 = 61.7425{\rm{;\;}}}\\{MSE = \frac{1}{{(I - 1)(J - 1)}} \cdot SSE = \frac{1}{{12}} \cdot 91 = 7.5833.}\end{aligned}\)

The value of test statistics are

\(\begin{aligned}{*{20}{c}}{{f_A} = \frac{{MSA}}{{MSE}} = \frac{{58.16}}{{7.5833}} = 2.5565}\\{{f_B} = \frac{{MSB}}{{MSE}} = \frac{{246.97}}{{7.5833}} = 8.1419}\end{aligned}\)

There are two ways to make conclusion. Using the table in the appendix or compute P value using a software.

04

value of test statistics PA and PB:

The PA value when testing hypotheses HOA versus HaA is

\({P_A} = P\left( {F > {f_A}} \right) = P(F > 2.5565) = 0.104\)

which was computed using software, and random variable F has Fisher's distribution with degrees of freedom\(I - 1 = 3{\rm{\;and\;}}(I - 1)(J - 1) = 12\)because

\({P_A} = 0.104 > 0.01 = \alpha \)

Do not reject hypothesis H0A

at given significance level. The true separation force is not affected by the angle of pull (which was required in the exercise). The PB value when testing hypotheses H0B versus HaB is

\({P_B} = P\left( {F > {f_B}} \right) = P(F > 8.1419) = 0.002\)

which was computed using software, and random variable F has Fisher's distribution with degrees of freedom\(J - 1 = 4{\rm{\;and\;}}(I - 1)(J - 1) = 12\)Because

\({P_B} = 0.002 < 0.01 = \alpha \)

Reject hypothesis H0B

at given significance level.

Using the fact

\({F_{\alpha ,I - 1,(I - 1)(J - 1)}} = {F_{0.01,3,12}} = 5.95,\)

which was obtained from the table in the appendix, and the fact that

\({F_{0.01,3,12}} = 5.95 > 2.5565 = {f_A}\)

Reject hypothesis H0A

at given significance level.

05

Values are estimated:

Finally, the result can be represented in a table

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