Question

At what age do infants speak their first word of English? Here are the data on 20 normal children (ages in months). Assume that the distribution of the age at which all children speak their first word (the population) is normal. 15 14 10 9 15 20 18 11 8 11 11 9 10 11 11 10 12 17 11 10 a) First, create a histogram of the data above using StatCrunch and include and attach it to your exam. Describe the shape. [2 points] b) Is there good evidence that the mean age at first word among all normal children is greater than 12 months? Conduct a hypothesis test at the α = 0.05 level of significance to determine this. [8 points] For full credit, make sure to show all 4 steps:

i) Hypothesize

ii) Prepare (level of significance and test that the conditions are met)

iii) Compute the test statistic and the p-value and include a sketch showing the p-value

iv) Write a sentence that interprets your results in context

Answer #1

In a sample of 77 children, the mean age at which the first
began to combine words was 16.51 months, with a standard deviation
of 9.59 months. Using a level of significance of 0.10, suppose we
want to test the claim that the mean age at which children first
begin to combine words is different from 14 months.
What is the claim of the problem?
What is the null hypothesis?
What is the alternative hypothesis?
What is the value of...

1.
A study of iron deficiency among infants compared samples of
infants following different feeding regimens. One group contained
breast-fed infants, while the children in another group were fed a
standard baby formula without any iron supplements. Here are the
summary results on blood hemoglobin levels at 12 months of age.
Mean
STD
Sample size
Breast-fed
13.3
1.7
23
Formula
12.4
1.8
19
Assume that the population variances
of the two groups are the same.
a.
Use the t-test to...

9.) How many commuters must be randomly selected to estimate the
mean driving time of Chicago commuters? We want 95% confidence that
the sample mean is within 3 minutes of the population mean, and the
population standard deviation is known to be 12 minutes.
A. 61 commuters
B. 8 commuters
C. 62 commuters
D. 7 commuters
10.) If we increase our sample size the width of the confidence
interval will
A. increase
B. stay the same
C. decrease
11.) Data...

Age and Price data for a sample of 12
cars
Age
(years)
5
4 5
5 7
6
6
2
7
7
8 9
Price(Hundreds)
95 100
75 82
89 98
66 95
179 72
49 84
At the 1%
significance level do the data provides sufficient evidence to
conclude that age and price of cars are negatively correlated. a)
Perform a hypothesis test ( 6 points)
State Null and alternative Hypothesis
Test Statistics
P-value approach
Conclusion:
Find the...

For Hypothesis testing and Decision making problems, please do
the following:
1. State the null and alternate hypothesis.
2. Write down the proper test statistic.
3. Show all calculations.
4. Show the critical value.
(5. State your conclusions.
1a. In a study of children with congenital heart disease,
researchers gathered data on age (in months) of ‘first’ walking
from 16 children with acyanotic heart disease. From larger studies
on normal children, the researchers know that mean age of walking
for...

The data on hospitalizations for swine flu are summarized in the
table below. Age Group Under 5 5 -14 15-29 30-44 45-60 Over 60
Total Hospitalized, Yes 8 12 13 15 0 1 49 Hospitalized, No 47 183
262 57 37 11 597 Total 55 195 275 72 37 12 646 Fill in the table
below with the expected counts if Age and Hospitalization are not
associated. Age Group Under 5 5 -14 15-29 30-44 45-60 Over 60 Total
Hospitalized,...

In an August 2012 Gallup survey of 1,012 randomly selected U.S.
adults (age 18 and over), 53% said that they were dissatisfied with
the quality of education students receive in kindergarten through
grade 12. Use the standard normal distribution to test if the
proportion of U.S. adults who are dissatisfied with the education
that students receive in kindergarten through grade 12 differs from
50%. The randomization distribution for this test is approximately
normal and the standard error is SE =...

The following data represent the number of training flight hours
that 18 pilot students receive from a certain instructor before
their first flight alone:
9 12 18 14 12 14 12 10 16
11 9 11 13 11 13 15 13 14
Perform a sign test at a significance level of 0.02 to test the
instructor's claim that the median training flight time required by
your students before flying alone is 12 hours.
Set the following
to. Null and alternative...

A dietary assessment was performed on 51 boys 9 to 11
years of age whose families were below poverty level. The mean
daily iron intake among these boys was found to be 12.50 mg with
standard deviation 4.75 mg. Suppose the mean daily iron intake
among a large population of 9 to 11 year old boys from all income
strata is 14.44 mg.
a. Conduct a 5 step significance test with alpha = .01 of whether
the mean iron intake...

The following table shows age distribution and location of a
random sample of 166 buffalo in a national park.
Age
Lamar
District
Nez Perce
District
Firehole
District
Row
Total
Calf
17
11
13
41
Yearling
12
11
10
33
Adult
31
31
30
92
Column Total
60
53
53
166
Use a chi-square test to determine if age distribution and
location are independent at the 0.05 level of significance.
(a) What is the level of significance?
State the null and...

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