Chapter 15 Flashcards
What are statistics?
a summary value that describes the sample.
mean of a sample and mean of a population
sample: x bar
population: mu
two general categories of statistical techniques:
descriptive and inferential statistics
Descriptive statistics are…
techniques that help describe a set of data.
The goal of descriptive statistics is to organize, summarize, and simplify data.
Inferential statistics are…
Inferential statistics help researchers determine when it is appropriate to generalize from a sample to a population.
-help determine if group/condition differences are from chance
organizing a set of scores into a graph or a table and calculating a single value, such as an average score, that describes the entire set is an example of what category of statistical techniques?
descriptive statistics
Summary values computed for a sample are called ___. The corresponding summary values for a population are called ____.
Summary values computed for a sample are called STATISTICS. The corresponding summary values for a population are called PARAMETERS.
What do frequency distributions demonstrate?
they demonstrate the number of instances a variable takes each possible value
What does each column in a frequency distribution table display?
The first column presents the SCALE OF MEASUREMENT, or simply lists the SET OF CATEGORIES INTO WHICH INDIVIDUALS HAVE BEEN ASSIGNED.
The second column lists the FREQUENCY, or the NUMBER OF INDIVIDUALS, located in each category.
In a frequency distribution graph, the ___ ___ _____ is along the horizontal axis and the _____ is on the vertical axis
In a frequency distribution graph, the SCALE OF MEASUREMENT is along the horizontal axis and the FREQUENCIES is on the vertical axis
2 options of graphing the frequency distribution
- HISTOGRAM: bar graph in which height of bars= frequency of occurrence of particular score. Adjacent bars touch eachother.
- POLYGON: scatterplot in which points are joined by straight lines. Height of dot above each score = frequency
When the categories on the scale of measurement are not numerical values ( NOMINAL or ORDINAL scales), the frequency distribution is presented as a ___ ___
bar graph
bar graph vs histogram
bar graph has spaces between bars.
Define “central tendency”
Statistical measure that identifies a single score that defines the center of distribution.
Its goal is to identify the value that is most typical or most representative of the entire group (single score that represents entire set)
What values measures central tendency?
mean, median, mode
What is the mean?
- measure of central tendency obtained by adding the individual scores, then dividing the sum by the number of scores.
- arithmetic average
What is the median?
-measure of central tendency which identifies the score that divides the distribution in half.
What is the mode?
measure of central tendency by identifying the most frequently occurring score in the distribution
The standard deviation uses the ___ of the distribution as a reference point and describes the _____ of the scores by measuring the distance between each ___ and the ____
The standard deviation uses the MEAN of the distribution as a reference point and describes the VARIABILITY of the scores by measuring the distance between each SCORE and the MEAN
When scores are clustered close to the mean, the standard deviation is ____
small
As a general rule, what percentage of the scores in a distribution are within a distance of 1 standard deviation of the mean? How many are 2 SDs from the mean? 3?
68% usually 1 SD from the mean, 95% usually 2 SDs from the mean, 99.7% is 3 SDs from the mean
The average squared distance from the mean is called ____
variance
How do you find the median in a distribution?
order scores from smallest to largest and find the middle value
In a negatively skewed distribution, where is the “tail” and “peak” of the graph?
the tail is pulled towards the left (negative). More scores are concentrated on the right (positive peak). Visa versa for positive skew