(ii) The two middle numbers are 480 and 530; when these are averaged, we obtain 505, or $505.
(iii) 5.66 and 5.05, respectively.
(iv) The average increases to $586 while the median is unchanged ($505).
A.2 (i) This is just a standard linear equation with intercept equal to 3 and slope equal to .2.
The intercept is the number of missed classes for a student who lives on campus.
(ii) 3 + .2(5) = 4 classes.
(iii) 10(.2) = 2 classes.
A.3 If price = 15 and income = 200, quantity = 120 – 9.8(15) + .03(200) = –21, which is nonsense.
This shows that linear demand functions generally cannot describe demand over a wide range of prices and income.
A.4 (i) The percentage point change is 5.6 – 6.4 = –.8, or an eight-tenths of a percentage point decrease in the unemployment rate.
(ii) The percentage change in the unemployment rate is 100[(5.6 – 6.4)/6.4] = –12.5%.
A.5 The majority shareholder is referring to the percentage point increase in the stock return, while the CEO is referring to the change relative to the initial return of 15%.
To be precise, the shareholder should specifically refer to a 3 percentage point increase.
A.6 (i) 100[42,000 – 35,000)/35,000] = 20%.
(ii) The approximate proportionate change is log(42,000) – log(35,000)
.182, so the approximate percentage change is %18.2.
[Note:
log(×) denotes the natural log.]
(ii) The approximate proportionate increase is .027(5) = .135, so the approximate percentage change is 13.5%.
(iii) 100[(45,935.80 – 40,134.84)/40,134.84) 14.5%, so the exact percentage increase is about one percentage point higher.
A.8 From the given equation, Dgrthemp = –.78(Dsalestax).
Since both variables are in proportion form, we can multiply the equation through by 100 to turn each variable into percentage form.
This leaves the slope as –.78.
So, a one percentage point increase in the sales tax rate (say, from 4% to 5%) reduces employment growth by –.78 percentage points.
A.9 (i) The relationship between yield and fertilizer is graphed below.
ANS of Introductory Econometrics A Modern Approach-Woolridge 4E.rar
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