A researcher selects a sample of n=25 individuals from a population with a mean of μ=60 and standard deviation of σ=10 and administers a treatment. The researcher predicts that the treatment will increase scores. Following the treatment, the average scores for this sample is M=65.

1. Using symbols, state the hypothesis for a one-tailed test.

2. Calculate the z-score and place this on a standardized normal distribution.

3. With a one-tail α=0.05, state the conclusion of these findings.

4. Calculate Cohen’s d and state the effect size (i.e., small, medium, large).

Consider a multiple-choice examination with 50 questions. Each question has four possible answers. Assume that a student who has done the homework and attended lectures has a 75% probability of answering any question correctly. A student must answer 43 or more questions correctly to obtain a grade of A. What percentage of the students who have done their homework and attended lectures will obtain a grade of A on this multiple-choice examination? A student who answers 35 to 39 questions correctly will receive a grade of C. What percentage of students who have done their homework and attended lectures will obtain a grade of C on this multiple-choice examination? A student must answer 30 or more questions correctly to pass the examination. What percentage of the students who have done their homework and attended lectures will pass the examination? Assume that a student has not attended class and has not done the homework for the course. Furthermore, assume that the student will simply guess at the answer to each question. What is the probability that this student will answer 30 or more questions correctly and pass the examination?

Is there a way to see this problem worked in Excel using the STDEV.S function? Would this be a one-tailed test or a two tailed test?

A claim is made that there is no correlation between comfort and price in luxury cars. A sample of 10 models of luxury cars were ranked according to their comfort levels and their prices. These ranks are given in the table below.

Model Comfort Price

A 9 10

B 3 9

C 2 7

D 7 1

E 5 3

F   1 6

G 8 8

H 10 5

I 6 2

J 4 4

Round your answers to 3 places after the decimal point, if necessary.

(a) Find the value of the (Spearman's) rank correlation coefficient test statistic.

(b) Find the critical values of (Spearman's) rank correlation coefficient if this test is conducted at the 0.02 significance level. Do not type " ± ± " in front of your answer (the ± ± is already given in front of the answer box below).

C. What is the correct conclusion of this test?

You decide to study the effect of GRE preparatory course on GRE score. Describe, in detail, how you will design your study, how you will collect data, and how you are going to statistically test whether the GRE course had an effect on GRE score. Be as specific as you can about your hypotheses. How would you, if at all, change your study if you decided to study the effect of the GRE preparatory course on graduate school admission instead?

7. A 95% confidence interval for the proportion of adults in Portland who have an iPhone is (0.303, 0.437). Find the number of people in the sample.7. A 95% confidence interval for the proportion of adults in BBC who have an iPhone is (0.303, 0.437). Find the number of people in the sample??

In order to estimate the mean 30-year fixed mortgage rate for a home loan in the United States, a random sample of 24 recent loans is taken. The average calculated from this sample is 6.80%. It can be assumed that 30-year fixed mortgage rates are normally distributed with a population standard deviation of 0.5%. Compute 95% and 99% confidence intervals for the population mean 30-year fixed mortgage rate. (Round intermediate calculations to at least 4 decimal places. Round "z" value to 3 decimal places and final answers to 2 decimal places. Enter your answers as percentages, not decimals.)

Confidence Level Confidence to Interval

95%.   ________% to  _______%

99%. ________% to  _______%

After years of rapid growth, illegal immigration into the United States has declined, perhaps owing to the recession and increased border enforcement by the United States (Los Angeles Times, September 1, 2010). While its share has declined, California still accounts for 35% of the nation’s estimated 11.3 million undocumented immigrants.

a. In a sample of 60 illegal immigrants, what is the probability that more than 21% live in California? (Round “z” value to 2 decimal places, and final answer to 4 decimal places.)

b. In a sample of 120 illegal immigrants, what is the probability that more than 21% live in California? (Round “z” value to 2 decimal places, and final answer to 4 decimal places.)

c. Comment on the reason for the difference between the computed probabilities in parts a and b.

• As the sample number increases, the probability of more than 21% also increases, due to the lower z value and decreased standard error.

• As the sample number increases, the probability of more than 21% also increases, due to the lower z value and increased standard error.

DATA 2

CORRELATION MATRIX

Comparing the zero order model and full model

1. Did the addition of X₂ and X₃ significantly increase R²? (correct answer is No,p>.01;Type II error is possible, please show me how to get there)

2. What is the adjusted R2 for the full model? (correct answer is 0.742, please show me how to do it)

Astronauts often report that there are times when they become disoriented as they move around in zero-gravity. Therefore, they usually rely on bright colors and other visual information to help them establish a top-down orientation. A study was conducted to assess the potential of using color for body orienting. 75 college students, reclining on their backs in the dark, found it difficult to establish orientation when positioned on under a rotating disk. This rotating disk was painted half black and half white. Out of the 75 students, 40 believed they were right side up when the white was on top. Use this information to estimate the true proportion of subjects who use the white color as a cue for right-side-up orientation. That is, construct a 95% confidence interval for the true proportion.

____≤?≤____

Each of the three new forms and the currently used form were filled out by 30 different people. The amount of time (in minutes) taken by each person to complete the task was recorded.

A) If the filling time of all IRS forms is distributed normally with mean of 102 and standard deviation of 8, what is the probability that a randomly selected person could do the tax forms in less than 90 minutes?

B) Referring to problem “A” above, If a randomly selected person is in the top 5 percent of the fastest people who do the tax forms, at least how many minutes should he spent to fill out the form?

Please Use your keyboard (Don't use handwriting) Thank you..

Courses Name: Introduction to Biostatistics PHC 121

Please answer the following questions:

***Please i need 500 words ..

I need new and unique answers, please. (Use your own words, don't copy and paste)

Q1. Discuss the tools to measure central tendency?

Q2.

a) Discuss parametric and nonparametric test used for    hypothesis testing.

    b) In a cross sectional study on coronary heart disease (CHD), the smoking and CHD status is summarized below. Use appropriate statistical test to conclude smoking plays any role in CHD.

***Please i need 500 words ..

I need new and unique answers, please. (Use your own words, don't copy and paste)

An investigator in the Statistics Department of a large university is interested in the effect of exercise in maintaining mental ability. She decides to study the faculty members aged 40 to 50 at his university, looking separately at two groups: The ones that exercise regularly, and the ones that don’t. There turn out to be several hundred people in each group, so she takes simple random sample of 25 persons from each group, for detailed study. One of the things she does is to administer an IQ test to the sample people, with the following results:

Regular Exercise:

Sample size: 25

Average score: 130

Standard deviation: 15

No Regular Exercise:

Sample size: 25

Average score: 120

Standard deviation: 15

The investigator concludes that exercise does indeed help to maintain mental ability among the faculty members aged 40 to 50 at his university. Is this conclusion justified? Explain whether you agree with her and show your reasoning mathematically

The following experiment was carried out to evaluate a drug for the prevention of heart attacks. The subjects were 3,900 middle-aged men with heart trouble. Out of these men, 1,100 were assigned at random to receive the drug, and the remaining 2,800 were given a placebo. The subjects were followed for five years. In the group that received the drug, there were 220 deaths; in the control group, 2 there were 588 deaths. The 220 is 20% of the treatment group and the 588 is 21% of the control group. Someone argues as follows: “A one-percentage-point difference may not seem like much, but 1% of a million, for example, is 10,000. The drug will save tens of thousands of lives.” Do you agree or disagree with the statement? Explain and show mathematically.

1. Consider rolling five dice. What is the probability of getting three ones (to 8 decimal places)?

2. Consider rolling five dice a single time each. What is the probability of rolling six ones?

II. Room Pricing in the Off-Season (Modeling)

The data in the table, from a survey of hotels with comparable rates on Hilton Head Island, show that room occupancy during the off-season (November through February) is related to the price charged for a basic room.

The goal is to use these data to help answer the following questions.

1. What price per day will maximize the daily off-season revenue for a typical hotel in this group if it has  rooms available?

2. Suppose that for this typical hotel, the daily cost is  plus  per occupied room. What price will maximize the profit for this hotel in the off-season?

The price per day that will maximize the off-season profit for this typical hotel applies to this group of hotels. To find the room price per day that will maximize the daily revenue and the room price per day that will maximize the profit for this hotel (and thus the group of hotels) in the off-season, complete the following.

1. Multiply each occupancy rate by  to get the hypothetical room occupancy. Create the revenue data points that compare the price with the revenue, , which is equal to price times the room occupancy.

2. Find an equation that models the revenue, , as a function of the price per day, .

3. Use maximization techniques to find the price that these hotels should charge to maximize the daily revenue.

4. Find a model for the occupancy as a function of the price, and use the occupancy function to create a daily cost function.

5. Form the profit function.

6. Use maximization techniques to find the price that will maximize the profit.