Question

1.  You want to obtain a sample to estimate how much parents spend on their kids birthday parties. Based on previous study, you believe the population standard deviation is approximately σ=26.2σ=26.2 dollars. You would like to be 99% confident that your estimate is within 2 dollar(s) of average spending on the birthday parties. How many parents do you have to sample?

2. You measure 27 watermelons' weights, and find they have a mean weight of 30 ounces. Assume the population standard deviation is 7.4 ounces. Based on this, what is the maximal margin of error associated with a 90% confidence interval for the true population mean watermelon weight.

Give your answer as a decimal, to two places

3.

Statistics students in Oxnard College sampled 11 textbooks in the Condor bookstore and recorded the number of pages in each textbook and its cost. The bivariate data are shown below:

Number of Pages (xx)	Cost(yy)
439	76.46
739	121.46
459	73.26
514	78.96
676	104.64
386	76.04
452	80.28
203	50.42
505	78.7
726	117.64
995	157.3

A student calculates a linear model
yy =  xx + . (Please show your answers to two decimal places)
Use the model to estimate the cost when number of pages is 949.
Cost = $ (Please show your answer to 2 decimal places.)

4.

Statistics students in Oxnard College sampled 11 textbooks in the Condor bookstore and recorded the number of pages in each textbook and its cost. The data are shown below:

Number of Pages (xx)	Cost(yy)
288	47.56
978	134.36
716	95.92
672	89.64
759	105.08
571	80.52
515	78.8
239	34.68
584	94.08
586	90.32
503	73.36

A student calculates a linear model using technology (TI calculator)
ˆyy^ =  xx + . (Please show your answers to two decimal places)
Use the model to estimate the cost when number of pages is 574.
Cost = $ (Please show your answer to 2 decimal places.)

Answer 1

Minitab output:

Regression Analysis: Cost(y) versus Number of Pages (x)

The regression equation is
Cost(y) = 16.13 + 0.14 Number of Pages (x)

Predictor                  Coef   SE Coef      T      P
Constant                    16.125     4.947   3.26 0.010
Number of Pages (x) 0.137476 0.008376 16.41 0.000

S = 5.68863   R-Sq = 96.8%   R-Sq(adj) = 96.4%

Analysis of Variance

Source          DF      SS      MS       F      P
Regression       1 8717.6 8717.6 269.39 0.000
Residual Error   9   291.2    32.4
Total          10 9008.8

(d)

Minitab output:

Regression Analysis: Cost(y) versus Number of Pages (x)

The regression equation is
Cost(y) = 9.77 + 0.13 Number of Pages (x)

Predictor               Coef   SE Coef      T      P
Constant               9.768     4.864   2.01 0.076
Number of Pages (x) 0.127417 0.007904 16.12 0.000

S = 5.17792   R-Sq = 96.7%   R-Sq(adj) = 96.3%

Analysis of Variance

Source          DF      SS      MS       F      P
Regression       1 6967.3 6967.3 259.87 0.000
Residual Error   9   241.3    26.8
Total               10 7208.6