Week 15a Experimental Methods and Measures of Central Tendency PDF

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Week 15a optional Silverstein class...

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Concepts — sections 1-2, 1-87 1-11, 1-12 experiment  a research method in which an investigator manipulates one or more factors (independent variables) to observe the effect on some behavior or mental process (the dependent variable). By random assignment of participants, the experimenter aims to control other relevant factors.  To find answers to such questions—to isolate cause and effect—researchers must experiment  Experiments enable researchers to isolate the effects of one or more factors by (1) manipulating the factors of interest and (2) holding constant (“controlling”) other factors. experimental group  in an experiment, the group exposed to the treatment, that is, to one version of the independent variable. control group  in an experiment, the group not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment. independent variable  in an experiment, the factor that is manipulated; the variable whose effect is being studied  We call this experimental factor the independent variable because we can vary it independently of other factors, such as the men’s age, weight, and personality. dependent variable  in an experiment, the outcome that is measured; the variable that may change when the independent variable is manipulated  Experiments examine the effect of one or more independent variables on some measurable behavior, called the dependent variable because it can vary depending on what takes place during the experiment. random assignment  assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between the different groups.  To minimize any preexisting differences between the two groups, researchers randomly assign people to the two conditions.  Random assignment—whether with a random numbers table or flip of the coin— effectively equalizes the two groups. operational definition  a carefully worded statement of the exact procedures (operations) used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures.

replication  repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding can be reproduced  Replication is an essential part of good science central tendency  numbers that are used to describe the center of a set of data. These measures include the mean median and mode mean  the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores. median  the middle score in a distribution; half the scores are above it and half are below it. mode  the most frequently occurring score(s) in a distribution. range  the difference between the highest and lowest scores in a distribution. variation  how similar or diverse the scores are  Averages derived from scores with low variability are more reliable than averages based on scores with high variability. (statistical) significance  a statistical statement of how likely it is that an obtained result occurred by chance  In short, when sample averages are reliable, and when the difference between them is relatively large, we say the difference has statistical significance  This means that the observed difference is probably not due to chance variation between the samples....