# inferential statistics

1. The Labor Bureau of USA wants to estimate, at a 90% confidence level, the

proportion of all households that receive welfare. The most conservative estimate of the sample size that would limit the maximum error to within .03 of the population

proportion is:

a. 1169

b. 927

c. 1391

d. 752 (ans)

2. The Labor Bureau of USA wants to estimate, at a 90% confidence level, the

proportion of all households that receive welfare. A preliminary sample showed that

16% of households in this sample receive welfare. The sample size that would limit

the maximum error of estimate to within .03 of the population proportion is:

a. 1091

b. 405 (ans)

c. 845

d. 1269

Show steps plz! :)

### 1 Answer

- 知足常樂Lv 76 years agoFavorite Answer
Please read:

圖片參考：https://s.yimg.com/rk/HA00430218/o/769961740.png

2014-04-20 00:23:17 補充：

中學數學：Completing the squares

p - p²

= 1/4 - 1/4 + 2(1/2)p - p²

= 1/4 - [ (1/2)² - 2(1/2)p + p² ]

= 1/4 - (1/2 - p)²

Any perfect square ≥ 0

(1/2 - p)² ≥ 0

-(1/2 - p)² ≤ 0

1/4 - (1/2 - p)² ≤ 1/4

2014-04-20 00:25:05 補充：

應該是中四學的：

y = x² + 6x + 10 = (x + 3)² + 1

Minimum of y is 1, the corresponding value of x is -3

That is, y = (x + 3)² + 1 ≥ 0 + 1 = 1