Question

10.

Following are closing prices of Google stock for a sample of trading days. Use the 1-Var Stats command in the TI-84 PLUS calculator to compute the sample standard deviation.

493.17 , 482.37, 483.19, 477.28 , 497.99, 475.10, 472.08, 444.95, 473.35

Write only a number as your answer. Round to two decimal places (for example: 8.32).

11.

In an English course, students had to turn in a final paper. The mean grade earned by the class was 81.2 with a standard deviation of 2.7 points. The scores are approximately bell-shaped. Approximately 68% of all final paper scores were between two values A and B. What is the value of A? Write only a number as your answer. Round to one decimal place.

12.

In a sample of Starbucks customers it was found that the number of individual items bought per month at Starbucks was 15 with a standard deviation of 17. Assume the data to be approximately bell-shaped. Approximately 95% of the time, the number of monthly items purchased was between two values A and B. What is the value of B? Write only a number as your answer.

13.

A study studied the birth weights of 1,729 babies born in the United States. The mean weight was 3234 grams with a standard deviation of 871 grams. Assume that birth weight data are approximately bell-shaped. Estimate the number of newborns who weighed between 1492 grams and 4976 grams. Write only a number as your answer. Round your answer to the nearest whole number.

14.

For a certain type of truck, the mean number of miles per gallon is 23.5 and the standard deviation is 4.3 . Assume gas mileage for this type of truck to be approximately bell-shaped. Compute the z-score for a truck whose gas mileage is 14 .

Write only a number as your answer. Round your answer to two decimal places (for example: 3.15).

15.

A population has mean 26 and standard deviation 8 . What is the data value that has a z-score of 1 ? Write only a number as your answer.

16.

Following is a sample of the number of words spoken in each inauguration address for U.S. presidents.

1,125

2,978
1,172
1,507
4,776
3,801
2,015
2,463
4,388
135
3,967
1,670
1,437
3,217
1,340
2,308
1,681
2,546
2,158
2,170
5,433
1,729
698

What is the 32nd percentile? Write only a number as your answer.

Answer 1

( 10 )

For the given data

X bar = 477.72

Create the following table.

data	data-mean	(data - mean)2
493.17	15.45	238.7025
482.37	4.65	21.6225
483.19	5.47	29.9209
477.28	-0.44000000000005	0.19360000000005
497.99	20.27	410.8729
475.10	-2.62	6.8644
472.08	-5.64	31.8096
444.95	-32.77	1073.8729
473.35	-4.37	19.0969

Find the sum of numbers in the last column to get.

∑(xi−X bar )² = 1832.9562

sample standard deviation ( s ) = sqrt (∑(xi− x bar)² / ( n-1 ))

= sqrt ( 1832.9562 / 8 )

= 15.1367

= 15.14

sample standard deviation ( s ) = 15.14

( 11 )

Given that

mean = 81.2 , standard deviation =  2.7

68% lies within one standard deviation from the mean

= ( 81.2 - 2.7 , 81.2 + 2.7 )

= ( 78.5 , 83.9 )

A = 78.5