Chapter 3 Understanding Validity. Importance of Validity Validity is the most important characteristic of any measurement.Validity is the most important.

1 Chapter 3 Understanding Validity ...
Author: Naomi Mathews
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1 Chapter 3 Understanding Validity

2 Importance of Validity Validity is the most important characteristic of any measurement.Validity is the most important characteristic of any measurement. Understanding validity can lead to an understanding of measurement and evaluation.Understanding validity can lead to an understanding of measurement and evaluation.

3 Types of Validity Construct validityConstruct validity Criterion validityCriterion validity Content validityContent validity Ecological validityEcological validity External validityExternal validity

4 Defining the Types of Validity Construct validity:Construct validity: –A correspondence exists between the constructs for a characteristic and the actual measurement being used to measure that characteristic. Criterion validity:Criterion validity: –A measure is believed to have sufficient validity that the error is acceptable for most uses; it is “close enough.” (continued)

5 More Types of Validity Content validity:Content validity: –Inspection shows that a measure logically appears to measure what it claims to measure. Ecological validity:Ecological validity: –The methods, materials, and setting of an experiment are similar to the real-life situation that is being measured. External validity:External validity: –A study’s results can be generalized to other situations and groups.

6 Your Viewpoint What constructs constitute physical fitness? According to your definition and constructs, do you consider yourself fit?What constructs constitute physical fitness? According to your definition and constructs, do you consider yourself fit? How do your friends, family, and classmates fare according to your list of constructs?How do your friends, family, and classmates fare according to your list of constructs?

7 Measures of Central Tendency— Descriptive Statistics MeanMean MedianMedian ModeMode

8 Mean Defined:Defined: –The average of a set of numbers in a distribution. Mean (average) = Σx n where Σx = the sum of all the numbers and n = the number of pieces of data. and n = the number of pieces of data.

9 Median Defined:Defined: –The middle number of a set of numbers in a distribution.

10 Mode Defined:Defined: –The most common number of a set of numbers in any distribution; also called the modal score.

11 Examples of Mean, Median, and Mode Assume a sample of 1, 2, 3, 3, 4, 5, 50 Mean = 9.7Mean = 9.7 Median = 3Median = 3 Mode = 3Mode = 3

12 Your Viewpoint What do you think of this statement:What do you think of this statement: –By cleverly choosing the way of presenting salary data, we may be able to influence state legislators regarding teacher pay raises. Is this manipulation of data fair?Is this manipulation of data fair?

13 Distributions Frequency distribution:Frequency distribution: –A way of organizing scores to show how often a particular score appears. Standard distribution:Standard distribution: –A common distribution of scores, also called normal distribution, when the mode lies right in the middle along with the mean and median.

14 Example of a Standard (Normal) Distribution

15 Mean, Median, and Mode in a Normal Curve

16 Standard Deviation Defined:Defined: –The measure of the variability in a distribution of scores, i.e., how close or far apart a group of numbers is.

17 A Normal Curve Showing the Standard Deviation

18 Calculating the Standard Distribution Use the following formula to calculate the SD by hand: SD=√(∑X 2 –((∑X) 2 /n))/(n–1) where ∑X 2 = the sum of the squared scores (∑X) 2 = the sum of the scores squared (∑X) 2 = the sum of the scores squared and n = the number of pieces of data and n = the number of pieces of data

19 Calculation of the Standard Deviation in Excel