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# Basic Data Analysis: Descriptive Statistics PowerPoint PPT Presentation

Basic Data Analysis: Descriptive Statistics. Types of Statistical Analysis. Descriptive Inferential: Test of Differences Test of Associative Predictive. Pre Descriptive Statistics. Data entry - Data coding (data code book). Data matrix

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Basic Data Analysis: Descriptive Statistics

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## Basic Data Analysis: Descriptive Statistics

### Types of Statistical Analysis

• Descriptive

• Inferential:

• Test of Differences

• Test of Associative

• Predictive

### Pre Descriptive Statistics

• Data entry - Data coding (data code book).

• Data matrix

• Descriptive statistics - “describe” the data, portray an average respondent (data reduction):

• Summarizes

• Conceptualizes

• Communication

• Interpolation/extrapolation

### Descriptive Statistics

• Statistical concepts:

• Measures of Central Tendency

• Measures of Variability

• Other Descriptive Measures

### Measures of Central Tendency

• Applies to any measure that reflects a typical or frequent response

• Mode: the number that appears most often

• Median: the value whose occurrence lie in the middle of a set of numbers (half above and half below)

• Mean: arithmetic average of a set of numbers

### Measures of Central Tendency

• Mean: arithmetic average of a set of numbers

X=sample mean

m = Population mean

### Measures of Variability

• Reveal the typical differences between values in a data set

• Frequency Distribution: tabulation of the number of times that each different value appears in a data set, shown as a percentage

• Range: difference between the lowest and highest value in a data set

### Measures of Variability

• Standard Deviation: indicates the degree of variation or diversity in the values in such as way as to be translatable into a normal curve distribution

• With a normal curve, the midpoint (apex) of the curve is also the mean and exactly 50% of the distribution lies on either side of the mean.

Normal, bell-shaped curve

50%

50%

Midpoint

(mean)

### Other Descriptive Measures

• Measures of skewness

• Is the curve really bell-shaped or does it “skew” to one side or the other?

• The closer the number given for skewness is to zero, the closer the distribution is to being bell-shaped.

• A positive skewness means that the distribution has a tail to the right while a negative skewness means it has a tail to the left

### Other Descriptive Measures

• Kurtosis indicates how pointed or peaked the distribution.

• A kurtosis value of zero or close to zero indicates that the distribution is bell-shaped.

### Microsoft Excel

• Menu: Tools, Data Analysis, Descriptive Statistics

• If Data Analysis is not present under Tools Bar then