Psychological Statistics 1-4

In an experimental study,

1 variable is measured and 2 groups are compared.

In a correlational study,

2 variables are measured and there is only 1 group of participants.

Correlational Research

2 variables are measured to determine whether there is a relationship.

What cannot be true for a distribution of scores?

60% of the scores are above the median.

A researcher surveys a sample of n = 200 college students and asks each person to identify his or her favorite movie from the past year. If the data were organized in a frequency distribution table, what would be listed in the first column?

A list of movies.

The normal distribution is an example of

A smooth curve showing data from a population.

Parameter

A value, usually a numerical value, that describes a population.

Statistic

A value, usually a numerical value, that describes a sample.

Ratio Scale

An interval scale with the additional feature of an absolute zero point. Ratios of numbers do reflect ratios of magnitude. Examples: Number of correct answers, time to complete task, gain in height since last year.

A sample has a mean of M = 86. If one new person is added to the sample, what effect will it have on the sample mean?

Cannot be determined by the information given.

What action will always change the value of the mean?

Changing the value of one score.

Ordinal Scale

Consists of a set of categories that are organized in an ordered sequence. Measurements on an ordinal scale rank observations in terms of size or magnitude. Examples: rank in class, clothing size, olympic medals, grades. Directional relationship.

Nominal Scale

Consists of a set of categories that have different names. Measurements on a nominal scale label and categorize observations, but do not make any quantitative distinctions between observations. Examples: race, gender, occupation, room numbers.

Interval Scale

Consists of ordered categories that are all intervals of exactly the same size. Equal differences between numbers on the scale reflect equal differences in magnitude. The zero point is arbitrary and does not indicate a zero amount on the variable being measured. Examples: IQ, Golf Scores Temperature

Organizing a set of scores in a table is an example of using _______.

Descriptive Statistics

A biologist records the number of trout, bass, perch, and other types of fish caught in a local lake during a 2-week period. If the results are organized in a frequency distribution table, what values would be listed in the first column?

Different types of fish.

Deviation

Distance from the mean.

Which types of graphs are used for data from an interval scale?

Histograms and Polygons

After measuring two individuals, a researcher can say that Tom's score is 4 points higher than Bill's. The measurements must come from a(n) _______ scale.

Interval or Ratio

In a population of N = 6, five of the individuals all have scores that are exactly 1 point above the mean.

It is below the mean by 5 points.

When to use mode?

Mode is the only option for describing central tendency for nominal data.

Does a discrete variable must be measured on a nominal or ordinal scale?

No, false.

Students in an introductory art class are classified as art majors and non-art majors. What scale of measurement is being used to classify the students?

Nominal

In a distribution with positive skew, scores with the highest frequencies are _____.

One the left side of the distribution.

Experimental Research

One variable is manipulated while another variable is observed and measured. To establish a cause-and-effect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results.

Determining the class standing (1st, 2nd, and so on) for the graduating seniors at a high school would involve measurement on a(n) _____ scale of measurement.

Ordinal

A researcher is curious about the average monthly cell phone bill for high school students in the state of Florida. If this average could be obtained, it would be an example of a ______.

Parameter

Variability

Provides a quantitative measure of the differences between scores in a distribution and describes the degree to which the scores are spread out or clustered together. Defined in terms of distance. Measures how well an individual score represents the entire distribution.

What kind of measurement scale is necessary to conclude that one score is twice a big as another?

Ratio

What scale of measurement is being used when a teacher measures the number of correct answers on a quiz for each student?

Ratio

A researcher uses an anonymous survey to investigate the television-viewing habits of American adolescents. Based on the set of 356 surveys that were completed and returned, the researcher finds that these students spend an average of 3.1 hours each day watching television. For this study, the set of 356 students who returned surveys is an example of a _______.

Sample

Although a research study is typically conducted with a relatively small group of participants known as a _________, most researchers hope to generalize their results to a much larger group known as a _________.

Sample; Population

The average verbal SAT score for the entire class of entering freshmen is 530. However, if you select a sample of 20 freshmen and compute their average verbal SAT score you probably will not get exactly 530. What statistical concept is used to explain the natural difference that exists between a sample mean and the corresponding population mean?

Sampling Error

Sample

Set of individuals selected from a population, usually intended to represent the population in a research study.

A characteristic, usually a numerical value, which describes a sample is called a _______.

Statistic

Descriptive Statistics

Statistical procedures used to summarize, organize, and simplify data.

For an experiment comparing two methods of teaching social skills training to autistic children, the independent variable is _______ and the dependent variable is _______.

Teaching methods; the social skills that are learned.

Interential Statistics

Techniques that allow us to study samples and them make generalizations about the populations from which they were selected.

Give an example of a continuous variable...

The amount of time to solve a problem.

Range

The distance covered by the scores in a distribution, from the smallest score to the largest score.

Population

The entire set of the individuals of interest for a particular research question.

Example of a discrete variable...

The gender of each student in a psychology class.

A recent study reports that students who just finished playing a prosocial video game were more likely to help others than students who had played a neutral or antisocial game. For this study, what is the independent variable?

The kind of game given to the students.

A researcher is measuring the amount of time needed to solve a set of anagrams for a sample of n = 15 students. However, one of the participants fails to solve the problems so the researcher has an undetermined score. What is the best measure of central tendency for these data?

The median.

Independent Variables

The variable being manipulated.

Dependent Variables

The variable being measured.

When to use median?

Time

A correlational study is used to examine the relationship between two variables but cannot determine whether it is a cause-and-effect relationship.

True

In a frequency distribution graph, frequencies are presented on the , and the scores (categories) are listed on the .

Y axis; X axis