Descriptive Statistics – Flashcards

Unlock all answers in this set

Unlock answers
question
What is descriptive statistics
answer
Descriptive statistics are used to describe the basic features of the data in a study. They provide simple summaries about the sample and the measures. ith descriptive statistics you are simply describing what is or what the data shows. Descriptive Statistics are used to present quantitative descriptions in a manageable form. In a research study we may have lots of measures. Or we may measure a large number of people on any measure. Descriptive statistics help us to simplify large amounts of data in a sensible way. Each descriptive statistic reduces lots of data into a simpler summary.
question
Characteristics of a single variable that we tend to look at:
answer
the distribution the central tendency the dispersion
question
The Distribution
answer
The distribution is a summary of the frequency of individual values or ranges of values for a variable. The simplest distribution would list every value of a variable and the number of persons who had each value.
question
Frequency distribution
answer
One of the most common ways to describe a single variable is with a frequency distribution. Depending on the particular variable, all of the data values may be represented, or you may group the values into categories first. The same frequency distribution can be depicted in a graph. This type of graph is often referred to as a histogram or bar chart. Distributions may also be displayed using percentages
question
The Central Tendency
answer
The central tendency of a distribution is an estimate of the "center" of a distribution of values. There are three major types of estimates of central tendency: Mean Median Mode
question
Mean
answer
To compute the mean all you do is add up all the values and divide by the number of values.
question
Median
answer
The Median is the score found at the exact middle of the set of values. One way to compute the median is to list all scores in numerical order, and then locate the score in the center of the sample. For example, if there are 500 scores in the list, score #250 would be the median. If Odd n, Middle Value of Sequence If Even n, Average of 2 Middle Values n+1/2=positioning point n=number of values
question
Mode
answer
The mode is the most frequently occurring value in the set of scores. To determine the mode, you might again order the scores as shown above, and then count each one. The most frequently occurring value is the mode.
question
Normal Distribution
answer
If the distribution is truly normal (i.e., bell-shaped), the mean, median and mode are all equal to each other.
question
The Dispersion
answer
Dispersion refers to the spread of the values around the central tendency. There are two common measures of dispersion, the range and the standard deviation.
question
The Range
answer
The range is simply the highest value minus the lowest value. In our example distribution, the high value is 36 and the low is 15, so the range is 36 - 15 = 21.
question
The Standard Deviation
answer
The Standard Deviation shows the relation that set of scores has to the mean of the sample.
question
Calculation of the Standard Deviation
answer
1. Find out the mean 2. Then for each number: subtract the Mean and square the results 3. Once you square them, sum them and divide this sum by the number of scores minus 1. Result is the variance. 4. Square root of the variance is the standart deviation
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New