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# Z-Test

### Statistics: IQ comparison of older vs. younger workers

IQ comparison of older vs. younger workers. the 1967 Age Discrimination in Employment Act made it illegal to discriminate against workers 40 years of age and older. Opponents of the law argue that there are sound economic reasons why employers would not wan tto hire and train workers who are very close to retirement. They a

### A study reported in "Inside Higher Education News" (May, 2006) found that financial incentives can improve low-income college students' grades and retention. As part of their "Opening Doors" program, a Louisiana community college offered to pay students \$1,000 per semester on condition that they maintain at least half-time enrollment and at least a 2.0 GPA.

Financial incentives for college students. A study reported in "Inside Higher Education News" (May, 2006) found that financial incentives can improve low-income college students' grades and retention. As part of their "Opening Doors" program, a Louisiana community college offered to pay students \$1,000 per semester on condi

### Calculating mean, standard deviation and z-score

Please help with the following statistics problem. Provide step by step calculations for each. You learned that 27% of all small business owned by non-Hispanic whites nationwide are women-owned firms. In a random sample of 350 small businesses owned by non-Hispanic whites, let x be the number that are owned by a woman. a)

### HOOPS: change in monthly sales

Hi, I need some guidance with this question: In the past, monthly sales for HOOPS, a small software firm, have averaged \$20,000 with standard deviation \$4000. During the last year sales averaged \$22,000 per month. Does this indicate that monthly sales have changed (in a statistically significant sense)? Use  0.05. Assu

### Finding Standardized Scores: Example Question

Given a mean of 60, with a standard deviation of 12, and with a raw score of 75, find (a) the z-score, (b) percentile rank, (c) t-score, (d) SAT score and (e) Stanine score Discuss why there are so many kinds of standardized scores.

### Influences on Z-Scores

How to explain the influences on z-scores with constant variables in hypothesis tests with (1) increasing differences between the sample mean and the original population mean, (2) increasing the population standard deviation, and (3) increasing the number of scores in the sample?

### Statistics: Fast food restaurant mean waiting time and correctly filed orders

Q-4a. You are the manager of a fast food restaurant. You want to determine whether the population mean waiting time to place an order has changed in the past month from its previous population mean value of 4.5 minutes. From past experience, you can assume that the population is normally distributed with a population standard

### Confidence Interval using Z Test for Mean and Proportion

See attached data file. Using the cumba file attached complete the following problems: Using the age data only. conduct a 95% confidence interval of the mean age of employees at Cumba Inc. Using the gender data only, conduct a 95% confidence interval of the proportion of female employees at cimab Inc. In one or two s

### Finding the Critical Value for a Z-Test.

Determine the critical region and critical values for z that would be used to test the null hypothesis at the given level of significance, as described in each of the following: Ho: mean less than or = to 82 and Ha:mean is greater than 82, a=0.10 Ho: mean=44 and Ha:mean is not equal to 44, a =0.01 Ho: mean greater t

### Mean and standard deviation measuring depression

Measuring depression: 100 students sampled; 30 men and 70 women. 4 were African American, 6 Hispanic and 1 Asian. 5 questions asked 1 =yes 0=no. The mean on the test was 3.5 with a standard deviation of 5. Billy scores 5 what is his standard score? Show work.

### Normal Distribution, Z-Score and Probability

In a recent year, about two-thirds of U.S. households purchased ground coffee. Consider the annual ground coffee expenditures for households purchasing ground coffee, assuming that these expenditures are approximately normally distributed as a normal random variable with a mean of \$45.16 and a standard deviation of \$10.00. 1.

### Statistics: Analyze Student Exam Scores

Students were given an exam with 300 multiple choice questions. The distribution of the scores were normal and the mean was 195 with a standard deviation of 30. you may find it helpful to draw out this distribution before answering the questions below 16. What were the scores of the students who were within one standard devia

### Statistics: 10 multiple choice questions

Find the area under the standard normal curve between z=0 and z=3. A. 0.4987 B. 0.9987 C. 0.4641 D. 0.0010 IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15. An individual's IQ score is found to be 110. Find the z-score corresponding to this value. A. -1.33 B. 1.33 C. -0.67

### Stanford-Binet IQ Test Scores: Distribution, z score, probability

Stanford-Binet IQ Test scores are normally distributed with a mean score of 100 and a standard deviation of 16. a. Sketch the distribution of Stanford -Binet IQ test scores. b. Write the equation that gives the z score corresponding to a Stanford-Binet IQ test score. Sketch the distribution of such z scores. c. Find the

### Test the hypothesis for proportions of red and brown M&Ms.

See attached file for M&M data. Test the hypothesis (± = 0.05) that the population proportions of red and brown are equal (pred = pbrown). You are testing if their proportions are equal to one another, NOT if they are equal to one another AND equal to 13%. NOTE: These are NOT independent samples, but we will use this approac

### Z-Score and Probability: Example Problem

Researchers at the University of Guelph sampled 344 business students and asked them this question: "over the course of your lifetime, what is the maximum number of years you expect to work for any one employer?" the sample resulted in mean, x = 19.1 years. Assume that the sample of students were randomly selected from the 6,000

### Standard Normal exercises, calculating expected values, exercises using binomial distribution

6 - 3 Problem 16 Assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation of 15 (as on the Wechsler test). (Hint: Draw a graph in each case.) Find the probability that a randomly selected adult has an IQ between 110 and 120 (referred to as bright normal). Problem 26 Use

### Purpose and Use of the Z-Score

I need to explain the z-score, the purpose of it, and how it works, to an individual that has the reading and comprehensive level of a 10 year old (4th grader). Can you give me at least two examples to help him understand,

### Statistics: Standard measure of hearing ability, Z scores

On a, the mean is 300 and the standard deviation is 20. Give the Z scores for persons who score (a) 340, (b) 310, and (c) 260. Give the raw scores for persons whose Z scores on this test are (d) 2.4, (e) 1.5, (f) 0, and (g) -4.5.

### Statistics: Z-score, sample standard deviation, standardized score

1. For a population with µ=50 and &#963;=10, A. What is the z-score for X=55, X=60, X=75, X=45, X=30 and X=35? B. Find the X value that corresponds to each of the following z-scores, z=1.00, z=0.80, z=1.50, z= -0.50, z= -0.30 and z= -1.50. 2. Find the z-score corresponding to a score of X=60 for each of the following dis

### Research: applied, basic, needs assessment, focus group, median, occurrence, z score

1. T F The only type of research in a business setting is applied research. 2. T F The ultimate purpose of basic research and applied research are identical.. 3. A needs assessment may include the following types of data: (a) Qualitative (b) Quantitative (c) Discrete (d) Continuous (e) All of the above 4. T F

### Create a frequency distribution, central tendency, variability, z-score

See attached file. Perform the following statistical operations on the "Height" data set forth in it using a Microsoft Word document: Create a frequency distribution Construct a frequency polygon and describe the shape of the distribution Calculate three measures of central tendency Calculate three measures of variabili

### Finding the P-Value: Tuberculosis Example

Medical tests were conducted to learn about drug-resistant tuberculosis. Of 142 cases tested in NJ, 9 were found to be drug-resistant. Of 268 cases tested in Tx, 5 were found to be drug-resistant. Do these data suggest a statistically significant difference between the proportions of drug-resistant cases in the 2 states? Use

### Test Statistic: Two sample Z test for Mean

A pharmaceutical company is testing the effectiveness of a new drug lowering cholesterol. As part of this trial, they wish to determine whether there is a difference between the effectiveness for women and for men. At a= 0.05 what is the test value? Women Men Sampl

### Statistics Exhibit 10-11: Insurance company samples of number of accidents

Exhibit 10-11 An insurance company selected samples of clients under 18 years of age and over 18 and recorded the number of accidents they had in the previous year. The results are shown below. Under Age of 18 Over Age of 18 n1 = 500

### Hypothesis Test for One Population Proportion Z test: 12.56 and 12.58

Use One-Proportion Z-Test 12.56 Christmas Presents. The Arizona Republic conducted a telephone poll of 758 Arizona adults who celebrate Christmas. The question asked was, "In your family, do you open presents on Christmas Eve or Christmas Day?" Of those surveyed, 394 said they wait until Christmas Day. a. Determine the

### Statistics: Z test for population proportion

Hypothesis test for the difference of population proportions Large companies typically collect volumes of data before designing a product, not only to gain information as to whether the product should be released, but also to pinpoint which markets would be the best targets for the product. Several months ago, I was interv

### Hypothesis test for the population mean: Z test for mean lifetime of light blubs

Hypothesis test for the population mean: Z test A manufacturer claims that the mean lifetime, mu, of its light bulbs is 44 months. The standard deviation of these lifetimes is 8 months. Ninety bulbs are selected at random, and their mean lifetime is found to be 43 months. Can we conclude, at the 0.05 level of significance, t

### Z-score corresponding to a score of X = 100 for distribution

How do you find the z-score corresponding to a score of X = 100 for the distributions given below? How do you know what direction they are going? a. mu = 80 and sigma = 10 b. mu = 80 and sigma = 5 c. mu = 105 and sigma = 10 d. mu = 105 and sigma = 5 Above, mu represents Mean and sigma represents Standard Deviation.

### Z Test for Comparison of Population Mean

See attached file. Based on the information given for each of the following studies, decide whether to reject the null hypothesis. For each, give (a) the Z-score cutoff (or cutoffs) on the comparison distribution at which the null hypothesis should be rejected, (b) the Z score on the comparison distribution for the samp