FINAL GUIDE

# FINAL GUIDE - FINAL EXAM Chapter 10 Statistics 1 2 3...

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FINAL EXAM: Chapter 10 : Statistics Understand the purpose of descriptive statistics o Statistics : mathematical methods to collect, organize, summarize, and analyze data. 1) Describe the data. 2) Describe the estimated accuracy of the data in representing the sampled population. 3) Describe how variables are related (this part comes in chapter 12). o Descriptive statistics : Intended to reduce data sets to allow for easier interpretation. These statistical methods allow organize data into some type of ordered fashion. We will be dealing with two types of descriptive statistics: data distribution and summary statistics. Understand data distribution and summary statistics (pp. 267-279) o Data distribution is most frequently in the form of tables and graphs. A distribution is simply a collection of numbers. Frequency distribution – a table of each score, ordered according to magnitude, and its actual frequency of occurrence. The sum of the frequency column is the number (N) of persons or items that make up the distribution. Some frequency distributions include the cumulative frequency (cf). Cumulative frequency – adding the number of scores in one interval to the number of scores in the intervals above it. o Sometimes it is best to present the data is graph form: Histogram/ bar chart: frequencies are represented in vertical bars. Frequency polygon : If a line is drawn from the midpoint of each interval at its peak along the y-axis to each adjacent midpoint/peak. Frequency curve : similar to a frequency polygon except the points are connected by a continuous, unbroken curve instead of a line. o Normal curve : a symmetrical bell-shaped curve. o Skewness : the concentration of scores around a particular point on the x- axis. If the tail trails off to the right it is known as a positive skew , and if the tail trails off to the left, it is known as a negative skew . - abscissa : x-axis (horizontal) - ordinate : y-axis (vertical) o Summary Statistics: Central Tendency o ** Summary statistics : help make data more manageable by measuring two basic tendencies of distribution: central tendency and dispersion, or variability. Central Tendency : describes a “typical” score. Mode = most frequently occurring score. Median = the score in the midpoint of the distribution. Mean (M) = the average of all the scores in a distribution. o Outliers : pull the mean toward their direction *Level of Distribution affects usefulness of central tendency measures (Nominal: Mode; Ordinal: Mode and Median; Interval/Ratio: Mode, Median, and Mean).

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o Summary Statistics: Dispersion Dispersion measures describe the way scores “spread out” away from the central tendency. Range
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FINAL GUIDE - FINAL EXAM Chapter 10 Statistics 1 2 3...

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