Turning Research Questions into Hypotheses Key Terms Flashcards
Comparison Distribution
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.
Conventional Levels of Significance (P <.05, P <.01)
Levels of significance widely used in psychology.
Cutoff Sample Score (Critical Value)
Point on the comparison distribution at which, if reached or exceeded by the sample score, you would reject the null hypothesis.
Directional Hypothesis
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.
Expected Relative Frequency
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.
Hypothesis Testing
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).
Hypothesis
Prediction, often based on informal observation, previous research, or theory, that is tested in a research study.
Long-Run Relative Frequency Interpretation of Probability
An understanding of probability as the proportion of a particular outcome you would get if the experiment were repeated many times.
Non-directional Hypothesis
Research hypothesis that does not predict a particular direction of difference between the population like the sample studied and the population general.
Normal Curve Table
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.
Normal Curve
A frequency distribution that is approximately symmetric and mound shaped, often called the Bell Curve.
Normal Distribution
A frequency distribution that follows a normal curve.
Null Hypothesis
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.
One-Tailed Test
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.
Outcome
The results of an experiment, or almost any event, such as a coin landing heads or it rains tomorrow.
Population Parameter
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.
Population
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.
Probability (P)
Expected relative frequency of an outcome; the proportion of successful outcomes to all outcomes.
Random Selection
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.
Raw Score
Ordinary score (or any number in a distribution before it has been made into a Z score or otherwise transformed).
Research Hypothesis
A statement about the predicted relationship between two populations (often a prediction of a difference between population means).
Sample Statistics
Descriptive statistic, such as the mean or standard deviation, figured from the scores in a group of people studied.
Sample
Scores of the particular group of people studied; usually considered to be representative of the scores in some larger population.
Statistically Significant
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.
Subjective Interpretation of Probability
A way of understanding probability as the degree of one’s certainty that a particular outcome will occur.
Theory
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.
Two-Tailed Test
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.
Z Score
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.
