Question

In a school district, all sixth grade students take the same standardized test. The superintendant of the school district takes a random sample of 26 scores from all of the students who took the test. She sees that the mean score is 121 with a standard deviation of 14.3688. The superintendant wants to know if the standard deviation has changed this year. Previously, the population standard deviation was 24. Is there evidence that the standard deviation of test scores has decreased at the α=0.05 level? Assume the population is normally distributed.

Step 1 of 5 : H0: σ≥24, Ha: σ<24

Step 2 of 5 : Determine the critical value(s) of the test statistic. If the test is two-tailed, separate the values with a comma. Round your answer to three decimal places.

Step 3 Determine the value of the test statistic. Round to 3 decimals

Step 4 Reject Null Hypothesis? or Fail to Reject Null Hypothesis?

Step 5 There is sufficient evidence to show that the variance of the share price is different than claimed? or There is not sufficient evidence to show that the variance of the share price is different than claimed?

Answer #1

A standardized test is given to a sixth grade class and a ninth
grade class. The superintendent believes that the variance in
performance from the sixth grade class is different than the
variance in performance from the ninth grade class. The sample
variance of a sample of 16 test scores from the sixth grade class
is 23.64. The sample variance of a sample of 10 test scores from
the ninth grade class is 14.9. Test the claim using a 0.05...

Colonial Funds claims to have a bond fund which has performed
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price is claimed to be 0.17 To test this claim, an investor
randomly selects 24 days during the last year to check the
performance of the fund. He finds an average share price of $15.80
with a standard deviation of 0.2113. Can the investor conclude that
the variance of the share price of the bond fund is different than...

A drug, which is used for treating cancer, has potentially
dangerous side effects if it is taken in doses which are larger
than 57.11mg, the required dosage for the treatment. It is
important that the variance of the amount of the active ingredient
is 0.01. 25 tablets are randomly selected and the amount of the
drug in each tablet is measured. It is determined that the variance
of the amount of active ingredient is 0.0023mg. Does the data
suggests at...

A standardized test is given to an eighth grade class and a
ninth grade class. The superintendent believes that the variance in
performance from the eighth grade class is smaller than the
variance in performance from the ninth grade class. The sample
variance of a sample of 15 test scores from the eighth grade class
is 31.01. The sample variance of a sample of 21 test scores from
the ninth grade class is 34.54. Test the claim using a 0.005...

If the quality of teaching is similar in a school, the scores on
a standardized test will have a standard deviation of 19. The
superintendent wants to know if there is a disparity in teaching
quality, and decides to investigate whether the standard deviation
of test scores has changed. She samples 22 random students and
finds a mean score of 110 with a standard deviation of 16.709. Is
there evidence that the standard deviation of test scores has
decreased at...

In a certain school district, it was observed that 25% of the
students in the element schools were classified as only children
(no siblings). However, in the special program for talented and
gifted children, 114 out of 386 students are only children. The
school district administrators want to know if the proportion of
only children in the special program is significantly different
from the proportion for the school district. Test at the α=0.05
level of significance.
What is the hypothesized...

In a certain school district, it was observed that 31% of the
students in the element schools were classified as only children
(no siblings). However, in the special program for talented and
gifted children, 78 out of 215 students are only children. The
school district administrators want to know if the proportion of
only children in the special program is significantly different
from the proportion for the school district. Test at the
α=0.01α=0.01 level of significance.
What is the hypothesized...

A standardized test is given to a sixth grade class and an
eleventh grade class. The superintendent believes that the variance
in performance for the two grades is different. The sample variance
of a sample of 11 test scores from the sixth grade class is 16.89.
The sample variance of a sample of 13 test scores from the eleventh
grade class is 13.78. Construct the 95% confidence interval for the
ratio of the population variances. Round your answers to four...

PLEASE DOUBLE CHECK ANSWER IS CORRECT & DON'T USE
HANDWRITTEN ANSWERS. THANK YOU!
If the quality of teaching is similar in a school, the scores on
a standardized test will have a standard deviation of 16. The
superintendent wants to know if there is a disparity in teaching
quality, and decides to investigate whether the standard deviation
of test scores has changed. She samples 26 random students and
finds a mean score of 186 with a standard deviation of 7.276....

in a certain school district, it was observed that 28% of the
students in the element schools were classified as only children
(no siblings). However, in the special program for talented and
gifted children, 98 out of 272 students are only children. The
school district administrators want to know if the proportion of
only children in the special program is significantly different
from the proportion for the school district. Test at the α = 0.02
level of significance. What is...

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