6. Two methods were used to measure the specific activity (enzyme activity per m

Question

6. Two methods were used to measure the specific activity (enzyme activity per mg of protein). avg S Method 1: 139 147 160 168 135 148 11.1 Method 2: 148 159 156 164 159 57 5.9 Is the mean of method i significantly different from the mean of method 2 at the 95% confidence level? 7. A previous study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. A coin counter manufacturer wishes to find the 99% confidence interval for the average weight of a nickel. How many nickels does he need to weigh to be accurate within 15 milligrams?

Explanation / Answer

H0: 1 - 2 = 0 i.e. (1 = 2)

H1: 1 - 2 0 i.e. (1 2)

            

Assuming population variances are equal, we would have to calculate pooled-variance t-Test

Sp^2= (n1-1)S1^2+(n2-1)S2^2/(n1-1)+(n2-1)

         = (7-1)*53.54^2+(7-1)*57.375^2/6+6

         = 36951.3314/12

         = 3079.27762

tSTAT=(X1-X2)-(µ1-µ2)/Sp^2(1/n1+1/n2)

       =(129.728571-135.557143)-0/3079.27762(1/7+1/7)

       =-5.8285714/29.661315

       =-0.1965

tCRIT is +/-2.18 and hence cannot reject the null hypothesis

Method 1 Method 2 139 148 147 159 160 156 168 164 135 159 148 157 11.1 5.9 129.7285714 135.5571429 Mean 53.54078552 57.37542613 Std Dev

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