Answer to Question #173588 in Statistics and Probability for ANJU JAYACHANDRAN

Question #173588

4. a) Plating of gold on wrist watches requires a chemical called . AiCI 3

Concentration of

the chemical that is added to the solution is an important factor. The objective is to

choose that concentration for which plating is uniform. Three concentration of AiCI 3

chosen were 5%, 15% and 20%. These were added in the solution and plating was

done and thickness (in units) measured on 5 samples is gives below.

Sample

Conc. of AiCI3

1 2 3 4 5

5% 3 2 4 2 4

15% 4 4 3 2 4

25% 3 3 4 4 2

Use ANOVA to comment on whether the concentration of AiCI gives same result or 3

not. (Use 05.0 α = )


1
Expert's answer
2021-05-07T11:39:03-0400

The given data is-



Let

HoH_o ​: The concentartion of Alcl3Alcl_3 gives same same results.

HaH_a ​:The concentartion of Alcl3Alcl_3 does not gives same same results.


The variance table is given by-




The combines sample size n=n1+n2+n3+n4n=n_1+n_2+n_3+n_4

=3+3+3+3+3=15=3+3+3+3+3\\=15


The number of samples K=5K=5


The mean of the combined sample-

xˉ=x1+x2+x3+x4+x55\bar{x}=\dfrac{x_1+x_2+x_3+x_4+x_5}{5}


=3.33+3+3.66+2.66+3.335=\dfrac{3.33+3+3.66+2.66+3.33}{5}


=14.7925=2.96=\dfrac{14.792}{5}=2.96


The Mean square for treatment(MST)-

=n1(x1xˉ)2+n2(x2x2ˉ)2+n3(x3x3ˉ)2+n4(x4x4ˉ)2+n5(x5x5ˉ)2k1=\dfrac{n_1(x_1-\bar{x})^2+n_2(x_2-\bar{x_2})^2+n_3(x_3-\bar{x_3})^2+n_4(x_4-\bar{x_4})^2+n_5(x_5-\bar{x_5})^2}{k-1}


=3(3.332.96)2+3(32.96)2+3(3.662.96)2+3(2.662.96)+3(3.332.96)251=\dfrac{3(3.33-2.96)^2+3(3-2.96)^2+3(3.66-2.96)^2+3(2.66-2.96)+3(3.33-2.96)^2}{5-1}


=3(0.1369+0.0016+0.49+0.09+0.1369)5=0.51324=\dfrac{3(0.1369+0.0016+0.49+0.09+0.1369)}{5}=0.51324



The Mean square for Error(MSE)-


=(n11)s12+(n21)s22+(n31)s32+(n41)s42+(n51)s52nK=\dfrac{(n_1-1)s_1^2+(n_2-1)s_2^2+(n_3-1)s_3^2+(n_4-1)s_4^2+(n_5-1)s_{5}^2}{n-K}


=(31)(0.0456)+(31)(0.00053)+(31)(0.163)+(31)(0.03)+(31)(0.0456)155=\dfrac{(3-1)(0.0456)+(3-1)(0.00053)+(3-1)(0.163)+(3-1)(0.03)+(3-1)(0.0456)}{15-5}


=2(0.0456+0.0053+0.163+0.03+0.0456)10=\dfrac{2(0.0456+0.0053+0.163+0.03+0.0456)}{10}

=0.0579=0.0579


Then, F=MSTMSEF=\dfrac{MST}{MSE}

=0.513240.0579=8.8642=\dfrac{0.51324}{0.0579}=8.8642


For Annova test the degree of freedom df1=n11=31=2df_1=n_1-1=3-1=2 and df2=nK=155=10df_2=n-K=15-5=10


The Tabulated value of F at degree of freedome 2 and 10 at 0.05 level of significance is 4.10


Conclusion: As The calculated value of F is greater than the tabulated F at 95% level of significance.

So HoH_o is rejected. Hence The concentartion of Alcl3Alcl_3 does not gives same same results


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