Basic Statistical Concepts

Four Scales of Measurement

• Nominal: categorical data
• Ordinal: rank order system
• Interval: differences in scores equal differences in amount measured
• Ratio: same as Interval, but adds the property of zero

Measures of Central Tendency

Mean

• add the total of all data
• count the amount of different sets of data
• take the total from step 1 and divide that digit by the total of step 2

Median is the score that falls directly in the middle of the total amount of data listed.

Mode is the number that shows up the most.

To find the range of a distribution, one must take the difference between the highest score and lowest score.

It is important, when looking a distribution of scores, to know how the scores are spread out. To do this, one must understand how to calculate the variance.

The variance is a concept that describes the spread of scores within a distribution. It is vital concept to grasp because it is directly related to standard deviation and the analysis of of data in the normal curve.

Standard Deviation

"Normal distribution, hypothetically represents the way test scores would fall if a particular test is given to every single student of the same age or grade in the population for whom the test was designed." (pg 46)

The normal curve also known as the bell curve describes many important facts about the population and test scores.

IQ scores are an example of how this information will be useful to a special education teacher.

68% of the population falls between 85 and 115 in regards to their IQ scores.

Gifted programs require and IQ score of at least 130

Statistics offers us as educators a way to compare children to the norms in multiple ways.

How this applies to my future as a special education teacher, is by providing me with the tools necessary to understand my students placement and comparison to the norms. It will also provide me with the means to make appropriate placement decisions for each student.