A computer software organization was encountering serious problems in predicting

Question

A computer software organization was encountering serious problems in predicting the man-day requirements for implementing large-scale programming projects. As part of a study on how to improve predictions, the company asked 24 programmers to predict the number of man-days for a large project about to be undertaken. The programmers were given full details about the specifications for the project. The programmers were classified by type of experience and amount of experience, and after the project was completed the forecasting errors were obtained. The forecasting errors (man-days predicted minus actual man-days) were: Amount of Experience (a) State the model you will use to analyze the effects of amount and type of experience on the forecasting error. (b) Test whether the factors have any main effects and whether they interact. Use a level of significance of .05 for each test. Write your ANOVA table. Summarize your results.

Explanation / Answer

(a) We should use 2-factor ANOVA

(b)

Since all the p- values are < 0.05, both the factors have main effects and the interaction is significant.

Two factor ANOVA Amount of experience Means: Under 2 years 2-5 years More than 5 years Small scale systems only 223.8 105.5 66.0 131.8 Type of experience Large scale systems 63.3 43.8 35.8 47.6 143.5 74.6 50.9 89.7 4 replications per cell ANOVA table Source SS    df MS F    p-value Amount of experience 42,504.17 1 42,504.167 104.95 6.15E-09 Type of experience 37,032.58 2 18,516.292 45.72 8.81E-08 Interaction 18,472.58 2 9,236.292 22.81 1.16E-05 Error 7,290.00 18 405.000 Total 105,299.33 23

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