BASIC STATISTICAL CONCEPTS Chapter Three

CHAPTER OBJECTIVES Scales of Measurement Measures of central tendency (mean, median, mode) Frequency distribution RangeVariance Standard Deviation Normal curve Skewed distribution Correlations Understand (and in some cases be able to calculate) the following:

SCALES OF MEASUREMENT In descriptive statistics, there are four scales of measurement that can be used to explain data: 1.NOMINAL 2.ORDINAL 3.INTERVAL 4.RATIO

NOMINAL Data created by assigning observations into various independent categories and then counting the frequency of occurrence within each of the categories.

ORDINAL A scale in which scores indicate only relative amounts or rank order

INTERVAL A scale in which equal differences in scores represent equal differences in amount of the property measured, but with an arbitrary zero point.

RATIO All the properties of an interval scale with the additional property of zero indicating a total absence being measured.

MEASURES OF CENTRAL TENDENCY MEANMEDIANMODE

FREQUENCY DISTRIBUTION Expresses how often a score occurs in a set of data.

RANGE The difference between the high score and the low score in the distribution VARIANCE A statistical concept that tells you the spread of scores within a distribution

STANDARD DEVIATION The spread of scores around the mean. Calculated by taking the square root of the variance.

NORMAL CURVE Also referred to as the bell curve Never changes NORMAL DISTRIBUTION Hypothetically represents the way test scores would fall if a particular test is given to every single student the same age or grade in the population for whom the test was designed.

SKEWED DISTRIBUTIONS A distribution in which the majority of scores fall at either the high end, or the low end rather than the middle of the distribution.

CORRELATIONS Tell us the relationship between two variables. There are three types: Positive Correlation Negative Correlation Zero Correlation

CHAPTER OBJECTIVES Scales of Measurement Measures of central tendency (mean, median, mode) Frequency distribution RangeVariance Standard Deviation Normal curve Skewed distribution Correlations Understand (and in some cases be able to calculate) the following:

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