Statisical Methods Appendix A.txt

The branch of applied mathematics that researchers use to organize, describe, and draw conclusions about the quantitative results of their studies

• Statistics used to organize, summarize, and describe data
• Includes measures of central tendency, variability, and relationships

• a measure or score that describes the center, or middle, of a distribution or scores
• Mean � the arithmetic average of a group of scores
• Median � the middle score or value when scores are arranged from highest to lowest
• Mode � the score that occurs most frequently in a group of scores

A bar graph that depicts the number of scores within each class interval in a frequency distribution

How much the scores in a distribution spread out away from the mean

The difference between the highest score and the lowest score in a distribution of scores

A descriptive statistic reflecting the average amount that scores in a distribution deviate, or vary, from their mean

• A symmetrical bell-shaped frequency distribution that represents how scores are normally distributed in a population
• Most scores fall near the mean, and fewer and fewer scores occur in the extremes above or below the mean
• 68% of scores in a normal distribution fall within 1 standard deviation of the mean (34.13% above and 34.13% below)
• Almost 95.5% of scores deviations above and
• 99.72% fall between above and below

A numerical value indicating the strength and direction of a relationship between two variable

A relationship between two variable in which both vary in the same direction

A relationship between two variable in which an increase in one variable is associated with a decrease in the other variable

• Statistical procedures based on probabilities that allow researchers to make inferences about the characteristics of the larger population from observations and measurements of a sample
• Estimates are derived of how much confidence can be placed in those inferences

The entire group of interest to researchers and to which they wish to generalize their findings; the group from which a sample is selected

The portion of any population that is selected for study and from which generalizations are made about the entire population

• Statistical tests that estimate the probability that a particular research result could have occurred by chance
• The estimates derived from tests are stated as probabilities
• A probability of .05 means that the experimental results would be expected to occur by chance no more than 5 times out of 100
• The .05 level is usually required as a minimum for researchers to conclude their findings are statistically significant

The process of repeating a study with different participants and preferably a different investigator to verify research