Turning Research Questions into Hypotheses Key Terms

Question 1

Comparison Distribution

Answer 1

Distribution used in hypothesis testing. It represents the population situation if the null hypothesis is true. It is the distribution to which you compare the score based on your sample’s results.

Question 2

Conventional Levels of Significance (P <.05, P <.01)

Answer 2

Levels of significance widely used in psychology.

Question 3

Cutoff Sample Score (Critical Value)

Answer 3

Point on the comparison distribution at which, if reached or exceeded by the sample score, you would reject the null hypothesis.

Question 4

Directional Hypothesis

Answer 4

Research hypotheses predicting a particular direction of difference between populations – for example, a prediction that the population like the sample studied has a higher mean than the population in general.

Question 5

Expected Relative Frequency

Answer 5

The number of successful outcomes of an experiment divided by the number of total outcomes that you would expect to get if you repeated the experiment a large number of times.

Question 6

Hypothesis Testing

Answer 6

Procedure for deciding whether the outcome of a study (results for a sample) supports a particular theory or practical innovation (which is thought to apply to a population).

Question 7

Hypothesis

Answer 7

Prediction, often based on informal observation, previous research, or theory, that is tested in a research study.

Question 8

Long-Run Relative Frequency Interpretation of Probability

Answer 8

An understanding of probability as the proportion of a particular outcome you would get if the experiment were repeated many times.

Question 9

Non-directional Hypothesis

Answer 9

Research hypothesis that does not predict a particular direction of difference between the population like the sample studied and the population general.

Question 10

Normal Curve Table

Answer 10

A table showing percentages of scores associated with the normal curve; the table usually includes percentages of scores between the mean and various numbers of standard deviations above the mean and percentages of scores more positive than various numbers of standard deviations above the mean.

Question 11

Normal Curve

Answer 11

A frequency distribution that is approximately symmetric and mound shaped, often called the Bell Curve.

Question 12

Normal Distribution

Answer 12

A frequency distribution that follows a normal curve.

Question 13

Null Hypothesis

Answer 13

Statement about a relation between populations that is the opposite of the research hypothesis; statement that in the population there is no difference (or a difference opposite to that predicted) between populations; a statistical hypothesis to be tested.

Question 14

One-Tailed Test

Answer 14

Hypothesis-testing procedure for a directional hypothesis; situation in which the region of the comparison distribution where the null hypothesis will be rejected is all on one side (tail) of the distribution.

Question 15

Outcome

Answer 15

The results of an experiment, or almost any event, such as a coin landing heads or it rains tomorrow.

Question 16

Population Parameter

Answer 16

Actual value of the mean, standard deviation, and so on, for the population; usually population parameters are not known, though often they are estimated based on information in samples.

Question 17

Population

Answer 17

The entire group of people to which a researcher intends the results of a study to apply; larger group to which inferences are made on the basis of the particular set of people (sample) studied.

Question 18

Probability (P)

Answer 18

Expected relative frequency of an outcome; the proportion of successful outcomes to all outcomes.

Question 19

Random Selection

Answer 19

A method for selecting a sample that uses truly random procedures (usually meaning that each person in the population has an equal chance of being selected); one procedure is for the researcher to begin with a complete list of all the people in the population and select a group of them to study using a table of random numbers.

Question 20

Raw Score

Answer 20

Ordinary score (or any number in a distribution before it has been made into a Z score or otherwise transformed).

Question 21

Research Hypothesis

Answer 21

A statement about the predicted relationship between two populations (often a prediction of a difference between population means).

Question 22

Sample Statistics

Answer 22

Descriptive statistic, such as the mean or standard deviation, figured from the scores in a group of people studied.

Question 23

Sample

Answer 23

Scores of the particular group of people studied; usually considered to be representative of the scores in some larger population.

Question 24

Statistically Significant

Answer 24

Conclusion that the results of a study would be unlikely if, in fact, the sample studied represents a population that is no different from the population in general; an outcome of hypothesis testing where the null hypothesis is rejected.

Question 25

Subjective Interpretation of Probability

Answer 25

A way of understanding probability as the degree of one’s certainty that a particular outcome will occur.

Question 26

Theory

Answer 26

A set of principles that attempt to explain one or more facts, relationships, or events; psychologists often derive specific predictions from theories that are then tested research studies.

Question 27

Two-Tailed Test

Answer 27

Hypothesis-testing procedure for a non-directional hypothesis; the situation in which the region of the comparison distribution where the null hypothesis would be rejected is divided between the two sides (tails) of the distribution.

Question 28

Z Score

Answer 28

Number of standard deviations that a score is above (or below, if it is negative) the mean of its distribution; it is thus an ordinary score transformed so that it better describes a score’s location in a distribution.