STA 2023 Practice TEST 2
#1 – 19 are worth 4 points each. #20 – 22 are worth 8 points each.
1) a) Statistics which use numerical or graphical summaries to characterize a set of data
are called _____________________statistics.
b) Statistics which use sample information to make conclusions or decisions about a
wider range of individuals are called ______________________ statistics.
2) a) An experiment in which neither the participants nor the researcher knows who is
receiving which treatment is called __________________________.
b) An experiment which has a person in the treatment group matched with a person in
the control group by attributes like gender or age is called _______________________.
3) In a sample of 250 people, 160 answered “yes”, 90 answered “no”, to whether they own a PC. What is the proportion of the sample that answered “yes”?
(Give answer as a decimal.) ______________________
4) What is the standard deviation of the proportion in #3? ______________________
(Show the formula, what you plug in, and round answer to the hundredths place.)
5) Find the sample size required for a study with a desired Margin of Error of 4% and a 95% confidence level. A pilot study had a standard deviation of 1.25.
(Show formula, plug-ins, and round appropriately) _______________________
For # 6 – 10, Find the
appropriate z-score or t-score.
Your answer should say “z = “ or “t = “ with z’s rounded to 2 decimal places & t’s rounded to 3 decimal places. Use a calculator screen if possible. Otherwise show the formula & your plug-ins.
6) m = 100. A random sample of 225 people has 
= 98.5 and 
= 15.
________________________
7) m = 100 and s = 15. An individual from a random sample of size 25 has a raw score of
132
________________________
8) p = 0.3 and a random sample has 50 out of 200. ________________________
9) A random sample of 64
subjects has = 77 and = 5. One student has a
score of 88.
________________________
10) A random sample of 16 data
values had = 50 and = 2.5. The population
has
m = 52.
_______________________
For # 11 – 12, use the appropriate formula & show your plug-ins to find the margin of error and the confidence interval. (Write your interval as an algebraic “between” expression.)
11) Times between uses of a TV remote control by males during commercials:
= 7.6 sec.; = 2.72 sec. ; 
= 150 ; 98% confidence interval (round to the nearest
hundredth.)
M.E. =________________________
C.I. __________________________
12) IQ scores of professional
athletes: 
= 12;
25; 99% confidence
interval (round to the tenths place.)
M.E.= _______________________
C.I.__________________________
For #13 – 15, use the appropriate calculator screen to find the confidence interval. Write your answer as an algebraic “between” expression.
13) Starting salaries of college graduates who have taken a Statistics course:
= $43,704;
= $9879; 100; 95% confidence interval (to the nearest dollar).
screen _______________________
C.I.__________________________
14) In a random sample of 1200, 800 answered “yes”. 90% confidence interval for the population proportion (round to thousandths place.)
screen _______________________
C.I.__________________________
15) 98%
confidence interval for 
, 
, and 
for a Statistics test.
(round to tenths place).
Screen_______________________
C.I._________________________
For # 16 – 18, tell which sampling method BEST describes each: Stratified; Cluster; Systematic; Convenience; or Random.
16) A list of all stockholders is compiled and every 50th name is selected.
________________________
17) Thirty hospitals are randomly selected and all cardiac patients in each hospital are surveyed about diet and exercise.
________________________
18) The
names of the 100
11 are drawn to form a committee.
________________________
19) What sample size is required for a proportion with a Margin of Error of 5% and a confidence level of 90%? A pilot sample had a proportion of 0.2.
(Show the formula & “plug-ins” and round appropriately.)
________________________
20) In 1990, 5.8% of job applicants failed the drug test. At the 0.02 significance level, test the claim that the failure rate is now lower if a random sample of 1520 current job applicants results in 58 failures.
Ho :__________________________
DRAW
IT!!
Ha :__________________________
One-tail or two-tail?_____________
Critical value:__________________
Calculated value: _______________
Reject Ho or Fail to reject Ho ?
_____________________________
Conclusion statement: _____________________________________________________
21) A survey of 400 students at a college found that 7% carry a gun, knife, or other such weapon. Use a = .05 to test the claim that 9% of all college students carry such weapons.
Ho :__________________________
Draw
it!!
Ha :__________________________
One-tail or two-tail?_____________
Critical value: _________________
Calculated value :______________
Reject Ho or Fail to reject Ho ?
_____________________________
Conclusion Statement:_____________________________________________________
22) A random sample of 1200 households with TV sets in use shows 264 were tuned to “60 Minutes”. Test the claim that more than 20% of viewers watch “60 Minutes” with a=.05.
Ho :_________________________
Draw
it!!
Ha :_________________________
One-tail or two-tail?____________
Critical value; _________________
Calculated value :______________
Reject Ho or Fail to reject Ho ?
____________________________
Conclusion Statement: ____________________________________________________