In: Statistics and Probability
#15
How productive are U.S. workers? One way to answer this question is to study annual profits per employee. A random sample of companies in computers (I), aerospace (II), heavy equipment (III), and broadcasting (IV) gave the following data regarding annual profits per employee (units in thousands of dollars).
| I | II | III | IV | 
| 27.3 | 13.2 | 22.7 | 17.9 | 
| 23.4 | 9.2 | 20.4 | 16.9 | 
| 14.3 | 11.5 | 7.2 | 14.8 | 
| 8.4 | 8.2 | 12.7 | 15.1 | 
| 11.8 | 6.5 | 7.0 | 10.2 | 
| 19.8 | 9.8 | 
(b) Find SSTOT, SSBET, and SSW and check that SSTOT = SSBET + SSW. (Use 3 decimal places.)
| SSTOT | = | |
| SSBET | = | |
| SSW | = | 
Find d.f.BET, d.f.W,
MSBET, and MSW. (Use 3 decimal
places for MSBET, and
MSW.)
| dfBET | = | |
| dfW | = | |
| MSBET | = | |
| MSW | = | 
Find the value of the sample F statistic. (Use 3 decimal
places.)
What are the degrees of freedom?
(numerator)
(denominator)
(f) Make a summary table for your ANOVA test.
| Source of Variation  | 
Sum of Squares  | 
Degrees of Freedom  | 
MS | F Ratio  | 
P Value | Test Decision  | 
| Between groups | NA | NA | ||||
| Within groups | ||||||
| Total | 
One Way Analysis of Variance (ANOVA)  
           
| I | II | III | IV | |||
| count, ni = | 5 | 6 | 5 | 6 | ||
| mean , x̅ i = | 17.040 | 11.40 | 14.00 | 14.12 | ||
| std. dev., si = | 7.990 | 4.752 | 7.307 | 3.39 | ||
| sample variances, si^2 = | 63.833 | 22.580 | 53.395 | 11.494 | ||
| total sum | 85.2 | 68.4 | 70 | 84.7 | 308.3 | (grand sum) | 
| grand mean , x̅̅ = | Σni*x̅i/Σni = | 14.01 | ||||
| square of deviation of sample mean from grand mean,( x̅ - x̅̅)² | 9.159 | 6.831 | 0.000 | 0.011 | ||
| TOTAL | ||||||
| SS(between)= SSB = Σn( x̅ - x̅̅)² = | 45.794 | 40.987 | 0.001 | 0.064 | 86.84558 | |
| SS(within ) = SSW = Σ(n-1)s² = | 255.332 | 112.900 | 213.580 | 57.468 | 639.280 | |
no. of treatment , k =   4
df between = k-1 =    3
N = Σn =   22
df within = N-k =   18
  
mean square between groups , MSB = SSB/k-1 =   
28.9485
  
mean square within groups , MSW = SSW/N-k =   
35.5156
  
F-stat = MSB/MSW =    0.8151
P value =   0.5022
---------------
| SSTOT | = | 726.126 | 
| SSBET | = | 86.8 | 
| SSW | = | 639.280 | 
| dfBET | = | 3 | 
| dfW | = | 18 | 
| MSBET | = | 28.949 | 
| MSW | = | 35.516 | 
value of the sample F statistic=0.815
(numerator) DF=3
(denominator) DF = 18
| ANOVA | ||||||
| Source of Variation | SS | df | MS | F | P-value | test decision | 
| Between Groups | 86.846 | 3 | 28.949 | 0.815 | >0.10 | do not reject Ho | 
| Within Groups | 639.280 | 18 | 35.516 | |||
| Total | 726.126 | 21 |