STAT 200 Week 5 Homework Problems
7.1.2
According to the February 2008 Federal Trade Commission report on
consumer fraud and identity theft, 23% of all complaints in 2007 were for
identity theft. In that year, Alaska
...
STAT 200 Week 5 Homework Problems
7.1.2
According to the February 2008 Federal Trade Commission report on
consumer fraud and identity theft, 23% of all complaints in 2007 were for
identity theft. In that year, Alaska had 321 complaints of identity theft out of
1,432 consumer complaints ("Consumer fraud and," 2008). Does this data
provide enough evidence to show that Alaska had a lower proportion of
identity theft than 23%? State the random variable, population parameter,
and hypotheses.7.1.6
The population proportion=0.23
n=number of complaints=1432
Alaska had complaints=321=x
So,
sample proportion=nx=1432321 =0.2242
H0: p=0.23 against H1: p<0.23
Z statistic,
Z=np^(1−p^)p^−0.23 ~N(0,1)
Obs(Z)=(-)0.52
H0: p=0.23 against H1: p<0.23
p value=0.30 (Excel Formula: NORM.S.DIST(0.52,1))
As,p value> α (level of significance). Hence there is not enough evidence to
support the claim that, Alaska had a lower proportion of identity theft than
23% .
Appropriate level of significance = 0.05
7.2.4
According to the February 2008 Federal Trade Commission report on
consumer fraud and identity theft, 23% of all complaints in 2007 were for
identity theft. In that year, Alaska had 321 complaints of identity theft out of
1,432 consumer complaints ("Consumer fraud and," 2008). Does this data
provide enough evidence to show that Alaska had a lower proportion of
identity theft than 23%? Test at the 5% level.
H0 : p = 0.23
μ=299,710.5 km/sec μ<299,710.5 lm/sec
H1 : p < 0.23
Z critical value = -1.645 at 5% level
Sample proportion
'p' = 321/1432 = 0.2242
Z stat = (p - P) / sqrt(PQ/n)
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= (0.2242 - 0.23) / sqrt(0.23*1-0.23/1432)= -0.52 Here - Z stat = -0.52 >
-1.645
Fail to reject Ho, therefore, there is no sufficient evidence of identity theft
lower than 23%.
7.2.6
In 2008, there were 507 children in Arizona out of 32,601 who were
diagnosed with Autism Spectrum Disorder (ASD) ("Autism and
developmental," 2008). Nationally 1 in 88 children are diagnosed with ASD
("CDC features -," 2013). Is there sufficient data to show that the incident of
ASD is more in Arizona than nationally? Test at the 1% level.
n=32601
x=507
Sample Proportion = 507/32601=0.0156
α=0.01
Ho:p=0.0114
Ha:p>0.0114
This corresponds to a right-tailed test, for which a z-test for one population
proportion needs to be used.
z=(0.0156-0.0114)/sqrt{(0.0114*[1-0.0114])/32601} = 7.061
Since the P-value is p=0, and p=0<0.01, it is concluded that the null
hypothesis is rejected. therefore, there is enough evidence to claim that the
population proportion p id greater than po, at the α=0.01 significance level.
7.3.6
The economic dynamism, which is the index of productive growth in dollars
for countries that are designated by the World Bank as middle-income are in
table #7.3.8 ("SOCR data 2008," 2013). Countries that are considered highincome have a mean economic dynamism of 60.29. Do the data show that
the mean economic dynamism of middle-income countries is less than the
mean for high-income countries? Test at the 5% level.
Table #7.3.8: Economic Dynamism of Middle Income Countries
25.805
7
37.451
1
51.915 43.695
2
47.850
6
43.717
8
58.076
7
41.164
8
38.079
3
37.725
1
39.655
3
42.026
5
48.615
9
43.855
5
49.136
1
61.928
1
41.954
3
44.934
6
46.052
1
48.365
2
43.625
2
50.986
6
59.172
4
39.628
2
33.607
4
21.664
3
Sample mean = 43.87 =AVERAGE(C2:I4,G5,F5,E5,D5,C5)
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Sample Standard Deviation = 9.7 =STDEV(C2:I4,G5,F5,E5,D5,C5)
n=26
Ho: μ=60.29
Ha: μ<60.29
α=0.05
t= (43.87-60.29)/(9.07/sqrt26)=-9.231
Critical value for a left tailed is tc=-1.708
since t=-9.231
18.125 α=0.05
Critical value for right tailed tc=1.86 t=(26.33-18.125)/(9.77/sqrt9) = 2.519
Since t=2.519>tc=1.86, it is concluded that the Ho is rejected. Therefore,
there is enough evidence to claim that the population mean is greater than
18.125 at a significance level of 0.05.
8.1.4
Suppose you compute a confidence interval with a sample size of 100. What
will happen to the confidence interval if the sample size decreases to 80?
The confidence interval will be larger because the smaller the sample is, the
further away from the true population.
8.1.8
In 2013, Gallup conducted a poll and found a 95% confidence interval of the
proportion of Americans who believe it is the government’s responsibility for
health care. Give the statistical interpretation. In 2013, Gallup conducted a
poll and found a 95% confidence interval of 0.52
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