Complete: Ch. 1 Problem Set

A cognitive scientist is interested in finding out which vocabulary test results in a smaller variance in vocabulary scores. She randomly splits a sample of children into two groups and uses one vocabulary test for one group; the other for the second group. She compares the test scores for each of the two groups.

Experimental

Which variable(s) in the data set are measured using a ordinal scale?

Gender Group

7. Identifying discrete and continuous variables

Suppose a researcher compiled a data set consisting of the following variables for a sample of 100 women. For each variable, select whether it is discrete or continuous.

Which variable(s) in the data set are measured using a ratio scale?

Temperature of Incubation, Number of Unhatched Eggs, and Gender Group

What is the sample in the study?

The 75 students who participated in the study

What is the population in the study?

The 750 first-year students at the college

Suppose the first subject scores 5 mph. Determine the real limits of 5. Lower limit Upper limit

- 4.5 - 5.5

Which of the following are variables in the study? Check all that apply.

- The students' self-assessment of their memory skills - The students' percentage of new unrelated words that were mistakenly thought to be on the original list

Researchers at a medical school conducted a study to test the effectiveness of a new treatment for lung cancer. Of the 128 lung cancer patients in an affiliated hospital, 94 volunteered for the new treatment, while the remaining 34 declined and underwent traditional treatment instead. The survival rates for the two treatment groups were measured after 12 months.

- a nonexperimental - dependent - quasi-independent

A researcher in a medical school would like to test the effectiveness of different insomnia treatments. She conducts a study on 120 volunteers, who are randomly assigned to five different insomnia treatment groups, one of which is a control group receiving a placebo. The number of hours slept per night is recorded for each participant over two weeks.

- an experimental - independent - dependent

In this experiment, the dependent variable is, [BLANK], and the independent variable is [BLANK]. The individuals who are in the control condition are typically referred to as the control group. Here the control group consists of [BLANK]. [BLANK] is a construct that is being tested in this experiment, and the experimenters have operationally defined it as [BLANK].

- functioning of the left hemisphere region of the brain - type of reading intervention - children who received the treatment typical in the community - functioning of the left hemisphere region of the brain - activity in the left hemisphere brain regions measured using an MRI

What is an example of a statistic in the study?

12%, the average percentage of new unrelated words that were mistakenly thought to be on the original list by the 75 students

When measuring weight on a scale that is accurate to the nearest 0.2 pound, what are the real limits for the weight of 131 pounds?

130.9 - 131.1

When measuring weight on a scale that is accurate to the nearest 0.1 pound, what are the real limits for the weight of 225 pounds?

224.95 - 225.05

2. Identifying populations, samples, statistics, parameters, and variables

A psychology professor wants to know whether confidence in memory skills is related to memory quality in current first-year students at his small college. Participants in the study (first-year students at his college) complete an online memory task. The students are first shown a list of 60 words. Next they are shown a list that includes five new words that are completely unrelated to words on the original list. Then they are asked to identify the words on the second list that appeared on the original list. He uses the percentage of new unrelated words that were mistakenly thought to be on the original list as his measure of memory quality. He also asks the students to report several characteristics such as their age, their gender, and a self-assessment of their memory skills. Each of the 750 first-year students (338 males and 412 females) at his school volunteered to participate. The professor chose 75 students at random to complete the memory task and answer the questions. The average percentage of new unrelated words that were mistakenly thought to be on the original list was 12%. The professor infers that if all 750 first-year students had completed the study, the results would show that an average of 12% (plus or minus sampling error) of new words were mistakenly identified as original words despite being completely unrelated to the words on the original list.

11. Statistical notation

Ask me ab it

Age

Continuous

Weight in pounds

Continuous

A professor interested in exercise and overall health collects questionnaire data from a sample of college students who use the gym in the campus center. Students in the sample indicate how many hours they spend at the gym and how often they go to the campus health center.

Correlational

A psychologist is interested in gender and cognition. She collects data on a large sample of siblings, recording their gender, birth order, and IQ.

Correlational

Highest grade completed

Discrete

The number of countries ever visited

Discrete

The number of television sets in the household

Discrete

What is an example of the professor using inferential statistics?

He infers that if all 750 students had done the experiment, the results would show that an average of 12% (plus or minus sampling error) of new words were mistakenly identified as original words despite being completely unrelated to the words on the original list.

What is an example of the professor using descriptive statistics?

He reports that the average percentage of new unrelated words that were mistakenly thought to be on the original list was 12%.

3. Distinguishing correlational and experimental research studies

In each of the following situations, data are obtained by conducting a research study. Classify each research study as Experimental or Correlational.

The values of data measured on this scale can be rank ordered. In addition, the differences between two adjacent ranks are equal.

Interval Scale

The values of data measured on this scale can be a number or a name, but they cannot be rank ordered.

Nominal Scale

The values of data measured on this scale can be a number or a name, but they can be rank ordered.

Ordinal Scale

Which of the following conclusions can you make on the basis of this study?

Positive affect is associated with a lower risk of coronary heart disease.

Values measured on this scale can be compared such that you can say, for example, one value is twice as big as another value.

Ratio Scale

5. Appropriate conclusions from experimental and nonexperimentalstudies

Researchers at the Columbia University Medical Center in New York conducted a study designed to investigate the relationship between positive emotions, which is known as positive affect, and coronary heart disease. Researchers measured the risk of coronary heart disease and the degree of expression of positive emotions of 1,739 healthy adults who participated in the study. The patients were then monitored for a period of 10 years for incidence of coronary heart disease. The researchers found that patients who displayed more positive affect had a lower risk of heart disease [Source: Eur Heart J (2010) 31(9):1065-1070].

10. Identifying the measurement scale of data

Scientists are looking at the effects of global warming on clutches (nests) of sea turtle hatchlings in different parts of the world. For a sample of clutches of turtle hatchlings, suppose that data were collected on the following variables: •Temperature of Incubation (as measured in kelvin) •Gender Group of Hatchling Clutch (0 = 0%; 1 = greater than 0% but less than or equal to 10% male; 2 = greater than 10% but less than or equal to 20% male; 3 = greater than 20% but less than or equal to 30% male; and so on) •Number of Hatched Turtle Eggs •Number of Unhatched Eggs •Location of Turtles (0 = west of North America; 1 = west of South America; 2 = tropical regions of Pacific Ocean; 3 = northwestern Atlantic; 4 = Indian Ocean) Recognizing the measurement scale of the data collected on each variable is important because the type of data dictates the appropriate data summary methods and statistical procedures.

9. Measurement scales matchup

Select the measurement scale in the right column that best matches the description in the left column. Note that each scale (nominal scale, ordinal scale, interval scale, and ratio scale) will be used exactly once.

6. Experiments, variables, and measurements

Shaywitz, Shaywitz, Blachman, and colleagues (2004) conducted an experiment to see whether a reading intervention based on phonetics could alter the functioning of the left hemisphere region of the brain to help children with reading disabilities read better. Some children (n = 37) were randomly assigned to receive the phonologically based reading intervention, whereas another group (n = 12) received the treatment that was typically used in their community. Children taught with the phonologically based reading intervention demonstrated increased activity in the left hemisphere regions of the brain during functional magnetic resonance imaging (MRI) compared with those who received the typical treatment. [Source: Shaywitz, B. A., Shaywitz, S. E., Blachman, B. A., et al. (2004). Development of left occipitotemporal systems for skilled reading in children after a phonologically-based intervention. Biological Psychiatry, 55(9), 926-933.]

What is an example of a parameter in the study?

The actual average percentage of new unrelated words that would be mistakenly recognized as being from the original list by the 750 first-year students.

4. Dependent and independent variables

The following research studies consist of two or more groups of scores being compared. For each, decide whether the study is experimental or nonexperimental, and then identify the dependent, independent, or quasi-independent variables.

12. Order of operations

There's a new PEMBAS 1. Perform any operation within parentheses. 2. Perform any exponentiation (such as squaring). 3. Perform any multiplication or division. 4. Perform any summations (Σ). 5. Complete any additional addition or subtraction in left to right order.

8. Real limits on continuous variables

You want to find out whether caffeine mitigates the effect of alcohol on reaction time. To study this, you administer to your subjects a drink that is equivalent to three 12-ounce beers, followed by the equivalent of two cups of coffee. Then your subjects complete a simulated driving task in which they must follow a fixed speed limit while driving on a straight road. Wind periodically and randomly pushes the simulated vehicle right, left, or not at all. Speed is measured in miles per hour above or below the 60-mph speed limit, with 1 mph being the smallest unit on the scale.

Which variable(s) in the data set are measured using a nominal scale?

location