Writers Den

PSY
315 Week 4 Practice Worksheet

Provide
a
response to the following questions.

Note:
Each team member should compute the following questions and submit to the
Learning Team forum. The team should then discuss each team member’s answers to
ascertain the correct answer for each question. Once your team has answered all
the questions, submit a finalized team worksheet.

1.
Two
boats, the Prada (Italy) and the Oracle (USA), are competing for a spot in the
upcoming America’s Cup race. They race over a part of the course several times.
The sample times in minutes for the Prada were as follows: 12.9, 12.5, 11.0,
13.3, 11.2, 11.4, 11.6, 12.3, 14.2, and 11.3. The sample times in minutes for
the Oracle were as follows: 14.1, 14.1, 14.2, 17.4, 15.8, 16.7, 16.1, 13.3,
13.4, 13.6, 10.8, and 19.0. For data analysis, the appropriate test is the t test: two-sample assuming unequal variances.

The next table shows the results of this
independent ttest. At the .05
significance level, can you conclude that there is a difference in their mean
times? Explain these results to a person who knows about the t test for a single sample but who is
unfamiliar with the t test for
independent means.

Hypothesis Test: Independent Groups (ttest, unequal variance)
	Prada	Oracle
	12.170	14.875	mean
	1.056	2.208	std. dev.
	10	12	n
		16	df
		-2.7050	difference (Prada – Oracle)
		0.7196	standard error of difference
		0	hypothesized difference
		-3.76	t
		.0017	p-value (two-tailed)
		-4.2304	confidence interval 95.% lower
		-1.1796	confidence interval 95.% upper
		1.5254	margin of error

2.
The
Willow Run Outlet Mall has two Haggar Outlet Stores, one located on Peach
Street and the other on Plum Street. The two stores are laid out differently,
but both store managers claim their layout maximizes the amounts customers will
purchase on impulse. A sample of 10 customers at the Peach Street store
revealed they spent the following amounts more than planned: $17.58, $19.73,
$12.61, $17.79, $16.22, $15.82, $15.40, $15.86, $11.82, $15.85. A sample of 14
customers at the Plum Street store revealed they spent the following amounts
more than they planned when they entered the store: $18.19, $20.22, $17.38,
$17.96, $23.92, $15.87, $16.47, $15.96, $16.79, $16.74, $21.40, $20.57, $19.79,
$14.83. For data analysis, a t test:
two-sample assuming unequal variances was used.

At the .01 significance level, is there
a difference in the mean amount purchased on an impulse at the two stores? Explain
these results to a person who knows about the t test for a single sample but who is unfamiliar with the ttest for independent means.

Hypothesis Test: Independent Groups (ttest, unequal variance)
	Peach Street	Plum Street
	15.8680	18.2921	mean
	2.3306	2.5527	std. dev.
	10	14	n
		20	df
		-2.42414	difference (Peach Street – Plum Street)
		1.00431	standard error of difference
		0	hypothesized difference
		-2.41	t
		.0255	p-value (two-tailed)
		-5.28173	confidence interval 99.% lower
		0.43345	confidence interval 99.% upper
		2.85759	margin of error

3.
Fry
Brothers Heating and Air Conditioning, Inc. employs Larry Clark and George
Murnen to make service calls to repair furnaces and air conditioning units in
homes. Tom Fry, the owner, would like to know whether there is a difference in
the mean number of service calls they make per day. Assume the population
standard deviation for Larry Clark is 1.05 calls per day, and 1.23 calls per
day for George Murnen. A random sample of 40 days last year showed that Larry
Clark made an average of 4.77 calls per day. For a sample of 50 days, George
Murnen made an average of 5.02 calls per day. At the .05 significance level, is
there a difference in the mean number of calls per day between the two employees?
What is the p-value?

Hypothesis Test: Independent Groups (ttest, pooled variance)
	Larry	George
	4.77	5.02	mean
	1.05	1.23	std. dev.
	40	50	n
		88	df
		-0.25000	difference (Larry – George)
		1.33102	pooled variance
		1.15370	pooled std. dev.
		0.24474	standard error of difference
		0	hypothesized difference
		-1.02	t
		.3098	p-value (two-tailed)
		-0.73636	confidence interval 95.% lower
		0.23636	confidence interval 95.% upper
		0.48636	margin of error

Week
4 Practice Worksheet PSY/315 Version 7