Statistics Practice Test Studies and Experiments

Name:______

Date:______Period:______

Chapter 11-12:Practice Test

Part 1: Multiple Choice. (2 points each)

Hand write the letter corresponding to the best answer in space provided on page 6.

__B___1. Which one of the following is not a principle of experimentation?

(a) Randomly allocating experimental units to treatments.

(b) Applying different treatments to males than females.

(d) Using a control group to determine whether treatment really works.

__D___2. In sample surveys, bias can be controlled by all of the following except

(a) Using a probability or chance sampling procedure.

(b) Wording questions so they are not confusing or misleading.

(d) Prompting respondents so that they give correct responses.

(e) Reducing non-response and undercoverage.

__C___3. In a study on the effect of reinforcement on learning from programmed text, two experimental treatments are planned: reinforcement given after every frame of programmed text or reinforcement given after every three frames. Which one of the following control groups would serve best in this study?

(a) A group which does not read the programmed text material.

(b) A group that reads the programmed material in prose formats.

(d) A group that reads the programmed text material and reinforcement is given at random.

(e) A group which watches the video of the programmed material.

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__C___4. A graduate student did a study to determine whether a new activity-based method is better than the traditional lecture of teaching statistics. He found two teachers to help him in his study for one semester. Mr. Dull volunteered to continue teaching with traditional lectures and Ms. Perky agreed to try the new activity-based method. Each teacher planned to teach two sections of approximately forty students each for adequate replication. At the end of the semester, all sections would take the same final exam and their scores would be compared. What is the treatment variable in this study?

(a) Teacher

(b) Section of the Course

(d) Final Exam Score

(e) Student

__C___5. Which of the following are true statements?

I. Voluntary response samples often underrepresent people with strong opinions.

II. Convenience samples often lead to undercoverage bias.

III. Questionnaires with nonneutral wording are likely to have response bias.

(a) I and II

(b) I and III

(d) I, II, and III

(e) None of the above gives the true set of responses.

__B___ 6. What fault do all these sampling designs have in common?

I. The Wall Street Journal plans to make a prediction for a presidential election based on a survey of its readers.

II. A radio talk show asks people to phone in their views on whether the United States should pay off its huge debt to the United Nations.

III. A police detective interested in determining a sample of high school students and interviews each one about any illegal drug use by the student during the past year.

(a) All the designs make improper use of stratification.

(b) All the designs have errors that can lead to strong bias.

(d) None of the designs satisfactorily controls for sampling error.

(e) None of the designs makes use of chance in selecting a sample.

__C___7. A study randomly assigned patients to treatment groups to determine the effect of taking aspirin in preventing colon polyps. One group took an aspirin daily and the other group took a placebo. Neither the patients nor the doctors knew who was getting which pill. This study is best described as a

(a) Blind experiment with random assignment

(b) Block design with random assignment

(d) Blinded block design observational study

(e) Randomly assigned observational study

__D__8. A researcher wishes to determine if watching 4 or more hours of TV per day adversely affects high school students’ academic performance. Which of the following designs is best?

(a) Study the records of randomly selected students

(b) Interview randomly selected students on their grades and TV habits

(d) Monitor the grades of students randomly placed into an under four-hour TV group and an over four-hour TV group

(e) Monitor the grades of students randomly placed into an under four-hour TV group, an over four-hour TV group and a no TV group

Use the following information to answer questions # 9-11

A personnel director at a large company studied the eating habits of employees by watching the movement of a selected group of employees at lunchtime. The purpose of the study was to determine the proportion of employees who buy lunch in the cafeteria, bring their own lunches, or go out to lunch

__C___9. The study would best be categorized as:

(a) A census

(b) A survey sample

(d) A designed experiment

(e) None of these

__B___10. If the director randomly selects a few departments and interviews all of the employees in those selected departments, she is performing a

(a) Simple random sample

(b) Cluster sample

(d) Multi-stage random sample

(e) Census

__B___11. If the director selects 40 females and 60 male employees at random (based upon the % in her company) throughout the company and categorizes their lunchtime practices by gender, she is:

(a) Blocking by gender

(b) Potentially testing for a lurking variable

(d) Testing for bias

__B,C___12. Which of the following is not a valid sample design?

(a) Code every member of a population and select 100 randomly chosen members

(b) Divide a population by ethnicity and select 50 individuals from each group

(MISSING RANDOM, ALSO ASSUMES ETHNIC GROUPS ARE SAME SIZE)

(SELECTION BIAS – UNDERCOVERAGE OF ALL OTHER STATES)

(d) Select five homerooms at random from all of the homerooms in a large high school

(e) All of these are valid

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Use the following excerpt from the random digit table to answer questions 15-17

21052 65031 45074 92846 67815

78231 01548 20235 56410 82713

__B___13. Which of the following statements regarding this excerpt of given random digits is true?

(a) The table can only be used for data coded with five-digit numbers.

(b) In order to use this table for a population of 100 names, the names could be coded 00 to 99; then distinct two-digit numbers would be selected sequentially to identify chosen names.

(d) This table can only be used if the data labels include all of the digits in the table.

(e) None of these statements is true.

__C___14. You have been given the task of determining if right-handed persons have stronger right hands than left hands. A sample of 10 right-handed persons is selected randomly. Which of the following designs would be most appropriate for this study?

(a) An observational study

(b) A design blocked for gender to determine if right-hand strength differs by gender

(c) A matched pair study in which each subject represents a block wherein the strength of the right hand and the left hand is measured in random order

(d) Five of the subjects and randomly placed in the control group and the other in the treatment group. All are tested and the results of each group are compared

(e) None of these is appropriate

__B___15. Which of the following is an example of a census?

(a) Every fifth person leaving a supermarket is asked to name his or her favorite brand of peanut butter.

(b) Each employee in a corporation fills out a questionnaire for a management survey.

(d) A telephone political poll selects ten names form every page of a city directory.

(e) All the commuters who are dissatisfied with the service of their commuter train company are asked to write a letter of complaint.

__D__ 16. Publishers of a magazine wish to determine what proportion of the magazine’s 50,000 subscribers are pleased with their subscription. The publishers intend to mail a survey to 1,000 subscribers randomly selected from those who have received the magazine for 5 years or more. This introduces selection bias, since long-subscribing customers are more likely to be pleased with their subscription. Which of the following would best eliminate selection bias?

(a) Mail surveys to 2,000 subscribers randomly selected from those who have received the magazine for 5 years or more.

(b) Mail surveys to 1,000 subscribers randomly selected from those who have received the magazine for 5 years or more and 1,000 subscribers randomly selected from those who have received the magazine for 1 year or less.

(d) Mail surveys to 1,000 subscribers randomly selected from all subscribers.

(e) Mail surveys to 500 subscribers randomly selected from a group who have received a free six-month subscription within the past year.

__A___17. Blocking is a technique used to (NOTE C IS NOT A BAD CHOICE, JUST NOT THE BEST)

(a) isolate the effect of treatment

(b) assist with random selection

(d) create stratified sample groups

(e) None of these

PART II - Answer completely, but be concise. Write sequentially and show all steps. Show all your work. Indicate clearly the methods you used, because you will be graded on the correctness of your methods as well as on the accuracy of your results and explanations.

1. In competitive sports, video recorders have been used more frequently in recent years. The idea behind the recorder is that coaches can replay training sessions for more effective feedback to the athlete. Some people believe video recording may make the athletes more nervous and actually decrease their performance. You have been asked to design an experiment to address this issue for competitive high school tennis players. You have decided to use the accuracy of tennis serves as your response variable, and the number of successful serves out of 100 as your performance measure. The subjects for your experiment are 60 high school male competitive tennis players of varying ability who have volunteered for the experiment.

a) Describe the treatments in your experiment. (4 points)

KNOWLEDGE AND ACTUALLY VIDEO RECORDING (ONE TREATMENT)

THE OTHER TREATMENT IS EITHER NOT VIDEO RECORDING, OR AT LEAST NO KNOWLEDGE OF VIDEO RECORDING (SECOND TREATMENT)

b) Create a completely randomized design experiment (6 points)

NO BLOCKING WHATSOEVER IS ALLOWED HERE…

RANDOMLY SELECT HALF TO GET ONE TREATMENT, HALF TO GET THE OTHER.. COMPARE SERVE PERCENTAGES IN EACH GROUP.

DIAGRAM IS GOOD HERE START WITH 60… 30 IN EACH TREATMENT THEN COME BACK TO A SINGLE BOX THAT SAYS COMPARE SERVE PERCENTAGE

c) One possible confounding variable is the experience levels of the players. Explain how you would control this variable? (4 points)

IDEALLY, MATCHED PAIR… ORDER OF TREATMENTS IS RANDOMIZED… COMPARE EACH PLAYER TO HIMSELF (SERVE %)

ALSO ACCEPTIBLE IS SKILL LEVEL OR YEARS OF EXPERIENCE BLOCKS, WHERE RANDOMIZED IN EACH BLOCK IS THE VIDEO OR NOT. CARRYOUT LIKE PART B FOR EACH BLOCK.

2. One of the tasks of wildlife biologists is to estimate bird populations. One method for doing this is to walk a “transect,” typically a long randomly selected rectangle, and count the number of particular species that are seen. During hunting season the biologists wear brightly colored clothes as a protective measure. A theory, known as the “species-confidence hypothesis,” predicts that birds may react to these brightly colored clothes. A robin, for example, when confronted with a biologist wearing an orange color may be less afraid than if the biologist were wearing a brown color. The idea is that the orange color gives the robin some “confidence” that the biologist is another (really big!) bird. This is a difficulty because a robin that is less afraid of the biologist may be easier to see and therefore “count” because the robin lets the biologist get closer. This would result in too high an estimate of the robin population. To test this theory a biologist performed a study in her area, wearing a bright orange vest or a brown vest while working. After training herself to accurately estimate distances she indicated on her notes how close the robins would let her get before they flew away (the “approach distance”), using this as a measure of their “confidence.” She randomly selected her starting points in each trip through the transects and also carefully noted the weather conditions, specifically the wind speed.

(a) What is the explanatory variable (factor) for this experiment? (4 points)

COLOR OF VEST

(b) What is the response variable for this experiment? (4 points)

APPROACH DISTANCE

(c) After completing the study the biologist was examining her results and noticed that on those days she wore the brightly-colored vest the wind tended to be of greater velocity. How does this information affect the interpretation of the results of the experiment? (4 points)

WIND IS CONFOUNDED WITH COLOR OF VEST – meaning you can’t tell whether it was the wind and/or the vest that was the reason for the change in approach. In fact (perfect response) the wind could help or hurt the approach distance and you would not know.

Confounded word is worth 1 pt. the discussion about two variables getting mixed together (2 pts). 1 pt for a good try.

3. The following paragraph describes an actual study. After reading the description, determine whether the study is an observational study or an experiment. Justify your answer with specific references to the information in the study. (6 points)

· Find 100 women age 30 of which 50 have been smoking a pack a day for 10 years while the other 50 have been smoke free for 10 years.

· Measure lung capacity for each of the 100 women.

· Analyze, interpret, and draw conclusions from data.

OBSERVATIONAL STUDY IS CORRECT. REASONS..

1. LACK OF CONTROL OVER LURKING VARIABLES, CONFOUNDING VARIABLES.

2. NO RANDOM ASSIGNMENT TO TREATMENT GROUPS

3. RETRO ASPECT…. ANALYZING PAST RECORDS IS OBSERVATIONAL. WHILE IT IS A CURRENT MEASUREMENT, IT TRANSFORMED INTO THE LUNG STATE IT IS IN OVER A LONG PERIOD OF 10 YEARS OR MORE.

Mr. Page Chapter 5 page 6