Chapter 2- Frequency Distributions: Lecture Flashcards
1
Q
Frequency Distributions
A
- Show how often each category of a variable occurs
- Organize and simplify the dataset
- Show where each case is located relative to others in the sample or population
2
Q
Frequency distribution tables
X-Column
A
- X Values from high to low
- only indicated values within range of your scores
3
Q
Frequency distribution tables
f column
A
- tallies (or frequencies) are determined for each value
- how often each X occurs in the data set
- the sum of the frequencies=N (population) or n (sample)
4
Q
Frequency distribution tables
Third column can be used for…
A
- Proportion (p) for each category: p=f/N, sum of p=1
- or Percentage corresponding to each X value: percentage=f/N times 100
5
Q
Regular frequency distribution
A
frequency distribution table that lists all x values individually
6
Q
Grouped frequency distribution
A
- frequency table that lists groups of scores (bc sometimes the list of X values is too long)
7
Q
Class intervals
A
- used in grouped frequency distribution tables
- intervals have the same width, and are usually a simple number (2, 5, 10, etc)
- Interval width is selected so that the table will have around 10 intervals
8
Q
frequency distribution graphs
A
- X values are listed on the X axis and Y values are listed on the y axis
- When the score categories (or variable of interest) are on an interval or ratio scale, graph should either be a histogram or polygon NOT a bar graph
9
Q
Histograms
A
- A bar is centered above each score (or class interval in the case of grouped data)
- Height of the bar corresponds to the frequency of individuals that endorsed that particular score (or whose score fell into that class interval)
- Bars touch bc it’s meaningful (numerical order)
- Captures data in a way where people can quickly understand what is going on
10
Q
Polygons
A
- a dot is centered above each score
- the height of the dot corresponds to the frequency
- dots are then connected by straight lines
- additional line is drawn at each end to bring the graph back to a 0 frequency (but not always)
11
Q
bar graphs
A
- used for x values on a nominal or ordinal scale
- just like a histogram except that gaps are left between adjacent bars
12
Q
smooth curve
A
- If scores or on the ratio or interval scale, it is customary to present distribution as a smooth curve rather than a jagged histogram or polygon
- emphasizes that the distribution is likely not showing the exact frequency for each category
- are useful because they show and summarize the entire set of scores
13
Q
At a glance, what can a smooth curve determine?
A
- the highest and lowest score
- where scores are centered
- whether scores are clustered or scattered
14
Q
smooth curves
the normal curve
A
- a symmetrical frequency distribution with the greatest frequency in the middle and frequencies decreasing as you move away from the middle in either direction
- frequently occurs in nature
15
Q
symmetrical distribution
A
- the left side is roughly a mirror image of the right
- Ex. hill shaped normal distribution
