GENG 2220
TO BE COMPLETED & SUBMITTED IN CLASS ONLY
Date: _______________
TUTORIAL #8: HYPOTHESIS TESTING
ID:
__________________________
PROBLEM 1
Name:
__________________________
The Edison Electric Institute (EEI) has published figures on the annual
number of kilowatt‐hours expended by various home appliances. It is
claimed that a vacuum cleaner expends an average of 47 kilowatt‐hours per year. If a random sample of 18 homes
included in a planned study indicates that vacuum cleaners use an average of 42 kilowatt‐hours per year with a
standard deviation of 10.5 kilowatt‐hours, does this suggest at the 0.05 level of significance that vacuum cleaners
used, on the average, less than 47 kilowatt‐hours annually? Assume the population of kilowatt‐hours to be
normally distributed.
A. Data from the problem
a. Sample size n =
b. Energy use (EEI estimates):
c. Energy use (actual):
d. Energy std. deviation (actual):
e. Level of significance α =
B. Hypotheses
Null hypothesis H0:
Alt. hypothesis H1:
C. Test statistic
D. Sketch (Graph)
E. Decision
GENG 2220
TO BE COMPLETED & SUBMITTED IN CLASS ONLY
Date: _______________
PROBLEM 2
In this class experiment, we will first estimate the proportion of the earth covered by water, and then we will apply
hypothesis testing to compare the result of our estimation with the actual proportion of water on earth.
A. Data collection: A globe ball will be tossed around the class. After grabbing the ball, make sure you hit the globe
with the tip of your right hand index finger (Without looking! You may also ask your neighbor at the table to
identify where your index finder has landed). Then, if your finger touched water, you should shout “WATER!” and if
your index finger touched land, you should shout “LAND!” After readout, throw the globe to another student in the
table next to you.
Number of students that hit the LAND
Number of students that hit the WATER
Estimate of % of earth surface covered by water
𝑤𝑎𝑡𝑒𝑟
× 100%
𝑤𝑎𝑡𝑒𝑟 + 𝑙𝑎𝑛𝑑
B. Find the information on earth surface water coverage using a search engine
Actual % of earth surface covered by water
C. Based on the output of our experiment, can it be concluded at the 0.05 level of significance that the proportion
of water on earth is __70.8_______% (Actual water proportion from part B)?
Null hypothesis H0:
Alternative hypothesis H1
Test statistic
Sketch
Decision
GENG 2220
TO BE COMPLETED & SUBMITTED IN CLASS ONLY
Date: _______________
PROBLEM 3
It is recommended that we visit the dentist for a cleaning every 10 months. To see whether or not patients are
adhering to this recommendation, a survey of 40 patients was conducted and it was determined that on average
patients visit the dentist every 10 months for a cleaning with a standard deviation of 1.5 month.
A. Determine whether patients are having regular cleanings every 10 months using traditional approach to
hypothesis testing. Use α=0.10.
B. In this context, what are the Type I and Type II errors?
C. Which type of error would be financially beneficial for dentists?
D. Do you think that α=0.10 is an appropriate significance level?