A standardized test is given to a sixth grade class. Historically, the test scores have had...
A standardized test is given to a sixth grade class. Historically, the test scores have had a standard deviation of 10. The superintendent believes that the standard deviation of performance may have recently changed. She randomly sampled 21 students and found a mean of 147 with a standard deviation of 15.2266. Is there evidence that the standard deviation of test scores has increased at the α=0.05 level? Assume the population is normally distributed.
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 of 5: Determine the value of the test statistic. Round your answer to three decimal places.
Step 4 of 5: Make the decision
Step 5 of 5: What is the conclusion?
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A standardized test is given to a sixth grade class.
Historically, the test scores have had...
A standardized test is given to a sixth grade class. Histo deviation of performance may have...
A standardized test is given to a sixth grade class. Histo deviation of performance may have recently changed. She randomly evidence that the standard deviation of test scores has increa rically, the test scores have had a standard deviation of 21. The believes that the standard sampled 30 students and found a mean of 160 with a standard deviation of 21.3846. Is there sed at the a 0.025 level? Assume the population is normally distributed Step 3 of 5: Determine...
If the quality of teaching is similar in a school, the scores on a standardized test...
If the quality of teaching is similar in a school, the scores on a standardized test will have a standard deviation of 29. 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 24 random students and finds a mean score of 163 with a standard deviation of 20.7366. Is there evidence that the standard deviation of test scores has decreased at...
If the quality of teaching is similar in a school, the scores on a standardized test...
If the quality of teaching is similar in a school, the scores on a standardized test will have a standard deviation of 2424. 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 2525 random students and finds a mean score of 145145 with a standard deviation of 10.215310.2153. Is there evidence that the standard deviation of test scores has decreased at...
In a school district, all sixth grade students take the same standardized test. The superintendant of...
In a school district, all sixth grade students take the same standardized test. The superintendant of the school district takes a random sample of 30 scores from all of the students who took the test. She sees that the mean score is 147 with a standard deviation of 38.7896. The superintendant wants to know if the standard deviation has changed this year. Previously, the population standard deviation was 26. Is there evidence that the standard deviation of test scores has...
A standardized test is given to a seventh grade class and an eleventh grade class. The...
A standardized test is given to a seventh 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 20 test scores from the seventh grade class is 29.56. The sample variance of a sample of 12 test scores from the eleventh grade class is 12.45. Construct the 90 % confidence interval for the ratio of the population variances. Round your answers to...
The manufacturers of Oriental Spice Sauce are concerned that the sodium levels in their product vary...
The manufacturers of Oriental Spice Sauce are concerned that the sodium levels in their product vary too much. A package of the sauce is supposed to contain 1000mg of sodium with a standard deviation of 150mg. A sample of 17 packages was analyzed and the sample standard deviation was 246.4609mg. Is there evidence at α=0.025 that the standard deviation of the sodium content exceeds the desired level? Assume the population is normally distributed. Step 1 of 5: State the null...
A standardized exam's scores are normally distributed. In a recent year, the mean test score was...
A standardized exam's scores are normally distributed. In a recent year, the mean test score was 1479 and the standard deviation was 316. The test scores of four students selected at random are 1880, 1220, 2180, and 1380. Find the z-scores that correspond to each value and determine whether any of the values are unusual. The z-score for 1880 is Round to two decimal places as needed.) The z-score for 1220 is (Round to two decimal places as needed) The...
1. Find the P-value for the indicated hypothesis test with the given standardized test statistic, z....
1. Find the P-value for the indicated hypothesis test with the given standardized test statistic, z. Decide whether to reject Upper H 0 for the given level of significance alpha. Two-tailed test with test statistic z= -1.95 and alpha=0.04 P-value= ? (Round to four decimal places as needed.) Reject H0 or fail to reject? 2. Find the critical value(s) for a left-tailed z-test with alpha=0.01. Include a graph with your answer. The critical value(s) is(are) ___ (Round to two...
1. A certain standardized test has scores which range from 0 to 500, with decimal scores...
1. A certain standardized test has scores which range from 0 to 500, with decimal scores possible. Scores on the exam are normally distributed with a mean of 301 and a standard deviation of 42. What proportion of students taking the exam receive a score greater than 366? Round your answer to 4 decimal places. 2.A certain standardized test has scores which range from 0 to 500, with decimal scores possible. Scores on the exam are normally distributed with a...
Suppose a new standardized test is given to 98 randomly selected third-grade students in New Jersey....
Suppose a new standardized test is given to 98 randomly selected third-grade students in New Jersey. The sample average score Y on the test is 57 points, and the sample standard deviation, sy, is 10 points. The authors plan to administer the test to all third-grade students in New Jersey. The 95% confidence interval for the mean score of all New Jersey third graders is ( 55.02, 58.98 ). (Round your responses to two decimal places.) Suppose the same test...
A standardized test is given to a sixth grade class. Histo deviation of performance may have recently changed. She randomly evidence that the standard deviation of test scores has increa rically, the test scores have had a standard deviation of 21. The believes that the standard sampled 30 students and found a mean of 160 with a standard deviation of 21.3846. Is there sed at the a 0.025 level? Assume the population is normally distributed Step 3 of 5: Determine...
A standardized test is given to a seventh 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 20 test scores from the seventh grade class is 29.56. The sample variance of a sample of 12 test scores from the eleventh grade class is 12.45. Construct the 90 % confidence interval for the ratio of the population variances. Round your answers to...
A standardized exam's scores are normally distributed. In a recent year, the mean test score was 1479 and the standard deviation was 316. The test scores of four students selected at random are 1880, 1220, 2180, and 1380. Find the z-scores that correspond to each value and determine whether any of the values are unusual. The z-score for 1880 is Round to two decimal places as needed.) The z-score for 1220 is (Round to two decimal places as needed) The...
Suppose a new standardized test is given to 98 randomly selected third-grade students in New Jersey. The sample average score Y on the test is 57 points, and the sample standard deviation, sy, is 10 points. The authors plan to administer the test to all third-grade students in New Jersey. The 95% confidence interval for the mean score of all New Jersey third graders is ( 55.02, 58.98 ). (Round your responses to two decimal places.) Suppose the same test...
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