QU1 Chapter 1.2 homework questions Flashcards
For population containing N=902 individuals, what code number would you assign for
a. the 1st person on the list
b. the 40th person on the list
c. the last person on the list
a. 001
b. 040
c. 902
Suppose you want to select a random sample of size 1 from a population of 3 items (which are called A, B, and C). the rule for drawing the sample is: Flip a coin; if it is heads, pick time A; if it is tails, flip the coin again; this time , if it is heads pick item B, if tails , choose C.. explain why this is a random sample but not a simple random sample.
This is a random sample because the selection is based on chance. It is not a simple random
sample because A is more likely to be selected than B or C.
A population has 4 members (call them A, B, C and D). you would like to draw a random sample of size 2, which you decide to do in the following This is a random sample because the selection is based on chance. It is not a simple random
sample because A is more likely to be selected than B or C. in the following way ; flip a coin, if it is heads, the sample will be items A and B; if it is tails, the sample will be items C and D. although this is a random sample, it is not a simple random sample.
Here all members of the population are equally likely to be selected and the sample selection
mechanism is based on chance. But selection of two elements is not independent; for
example, if A is in the sample, we know that B is also, and that C and D are not.
a company uses prenumbered sales invoices. the invoices are numbered from 0001 to 5000.
a. beginning in row 16, column 1, and proceeding horizontally in table 3.1, select a simple random sample of 50 invoice numbers.
Row 16: 2323 6737 5131 8888 1718 0654 6832 4647 6510 4877
Row 17: 4579 4269 2615 1308 2455 7830 5550 5852 5514 7182
Row 18: 0989 3205 0514 2256 8514 4642 7567 8896 2977 8822
Row 19: 5438 2745 9891 4991 4523 6847 9276 8646 1628 3554
Row 20: 9475 0899 2337 0892 0048 8033 6945 9826 9403 6858
Row 21: 7029 7341 3553 1403 3340 4205 0823 4144 1048 2949
Row 22: 8515 7479 5432 9792 6575 5760 0408 8112 2507 3742
Row 23: 1110 0023 4012 8607 4697 9664 4894 3928 7072 5815
Row 24: 3687 1507 7530 5925 7143 1738 1688 5625 8533 5041
Row 25: 2391 3483 5763 3081 6090 5169 0546
Note: All sequences above 5000 are discarded. There were no repeating sequences.
LOOK AT SHEET FOR CORRECT ANSWER
a company uses prenumbered sales invoices. the invoices are numbered from 0001 to 5000.
b. select a systematic sample of 50 invoice numbers. use the random numbers in row 20, columns 5-7 , as the starting point for your selection
k =
N
n
=
5,000
50
= 100
089 189 289 389 489 589 689 789 889 989
1089 1189 1289 1389 1489 1589 1689 1789 1889 1989
2089 2189 2289 2389 2489 2589 2689 2789 2889 2989
3089 3189 3289 3389 3489 3589 3689 3789 3889 3989
4089 4189 4289 4389 4489 4589 4689 4789 4889 4989
SEE SHEET FOR CORRECT ANSWER
a company uses prenumbered sales invoices. the invoices are numbered from 0001 to 5000.
c. are the invoices selected in (a) the same as those selected (b)? why or why not?
With the single exception of invoice #0989, the invoices selected in the simple random
sample are not the same as those selected in the systematic sample. It would be highly
unlikely that a random process would select the same units as a systematic process
Suppose that 4000 sales invoices are separated into 4 strata. Stratum 1 contains 50 invoices; Stratum 2 contains 500 invoices, stratum 3 contains 1000 invoices, and strum 4 contains 3450 invoices. all 50 invoices in stratum 1 are to be selected, and 50 invoices from each of the other strata are to be selected
a. what type of sampling should be done? Why?
The proposed sample design is a nonprobability quota sample. Since the invoices are
already separated into strata, a stratified sample should be used to reduce selection bias
and improve generalizability of results.
Suppose that 4000 sales invoices are separated into 4 strata. Stratum 1 contains 50 invoices; Stratum 2 contains 500 invoices, stratum 3 contains 1000 invoices, and strum 4 contains 3450 invoices. all 50 invoices in stratum 1 are to be selected, and 50 invoices from each of the other strata are to be selected
b. explain how you would carry out the sampling according to the method stated in (a) quota sample
Sampling 4% of the invoices in each of the four strata would produce a sample with the
same number of units
Suppose that 4000 sales invoices are separated into 4 strata. Stratum 1 contains 50 invoices; Stratum 2 contains 500 invoices, stratum 3 contains 1000 invoices, and strum 4 contains 3450 invoices. all 50 invoices in stratum 1 are to be selected, and 50 invoices from each of the other strata are to be selected
c. why is the type of sampling in (a) quota not a simple random sample
The proposed sample design is not a simple random sample because all invoices do not
have an equal chance of being selected.
A simple random sample of n = 300 full time employees is drawn form a company list containing the names of all N=5000 full time employees in order to evaluate job satisfaction.
a. give an example of possible coverage error
Possible coverage error: Only employees in a specific division of the company were
sampled.
A simple random sample of n = 300 full time employees is drawn form a company list containing the names of all N=5000 full time employees in order to evaluate job satisfaction.
b. give an example of possible nonresponse error
Possible nonresponse error: No attempt is made to contact nonrespondents to urge them
to complete the evaluation of job satisfaction.
A simple random sample of n = 300 full time employees is drawn form a company list containing the names of all N=5000 full time employees in order to evaluate job satisfaction.
c. give an example of possible sampling error
Possible sampling error: The simple random sample included a significantly higher
proportion of female employees than the company list of full-time employees indicated.
A simple random sample of n = 300 full time employees is drawn form a company list containing the names of all N=5000 full time employees in order to evaluate job satisfaction.
d. give an example of possible measurement error
Possible measurement error: The person collecting and analyzing the job satisfaction
information has a major impact on the company’s merit pay decisions.
