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 |