Question

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se of Exercise 14.4, the analyst measured the elapsed 243 sure read operatioompl44 of num In the second phase the In ond phas of the complexity of the query. The complexity was functf keywords in the query. The number of disk- Exerci also measured, as shown in Table 14.5. For this models to predict the elapsed time as a function re regression re data imber of keywords and interpret the result obtained sented in 4.5 Dabase Performance as a Funetion of TABLE Number of Keywords r formula swer the Elapsed Time 0.75 0.70 0.80 1.28 1.60 Number of Disk Reads Number of 78 92 h a CPU 16 to take easured

Answer 1

Question asked:

For this data prepare regression models to predict the elapsed time as a function of number of keywords and interpret the results

Answer :
(1) To fit regression line to predict the elapsed time as a function of number of keywords:

X	Y	XY	X2
1	0.75	0.75	1
2	0.70	1.4	4
4	0.80	3.2	16
8	1.28	10.24	64
16	1.60	25.6	256
Total = 31	5.13	41.19	341

So,

the Regression Line is given by:

(2) Interpretation:

(i) Slope = 0.063. : If the time t increases by 1, the number of keywords increases by 0.063.

(ii) Intercept = 0.065: At the beginning of the query (i.e., at t = 0), the number of keywords = 0.063. This interpretation of the intercept does not make sense in the real world. So, we ignore interpretation of slope in this case.