Week 8 ETEC 668 Quantitative Research in Educational Technology

Dr. Seungoh PaekMarch 5, 2014

Using Inferential Statistics

Linear Regression

How Inference Works

A representative sample of the population is chosen.

A test is given, means are computed and compared

A conclusion is reached as to whether the scores are statistically significant

Based on the results of the sample, an inference is made about the population.

What is Prediction All About?

Correlations can be used as a basis for the prediction of the value of one variable from the value of another– Correlation can be determined by using a set of

previously collected data (such as data on variables X and Y)

– calculate how correlated these variables are with one another

– use that correlation and the knowledge of X to predict Y with a new set of data

The Logic of Prediction

Prediction is an activity that computes future outcomes from present ones– What if you wanted to predict college GPA based

on high school GPA?

Scatter Plot

Regression Line

Regression line – reflects our best guess as to what score on the Y variable would be predicted by the X variable.– Also known as the “line of best fit.”

Prediction of Y given X = 3.0

Error in Prediction

Prediction is rarely perfect…

Drawing the World’s Best Line

Linear Regression Formula– Y=bX + a

Y = dependent variable– the predicted score or criterion

X = independent variable– the score being used as the predictor

b = the slope – direction of the line

a = the intercept– point at which the line crosses the y-axis

Let’s try predicting…

Let’s use PSPP to compute the regression line in predicting Y from X

We’ll use the number of hours of training to predict how severe injuries will be if someone is injured playing football

Variable Definition

Training (X) # of hours per week of strength training

Injuries (Y) Severity of injuries on a scale of 1 to 10

Using the Computer

SPSS and Linear Regression

SPSS Output

What does it all mean?

Y = -.13 X + 6.85

Scatterplot

Data Analysis Procedures

February 27, 2013

Where are we now?

Identified a problem focus Outlined literature review Stated research questions

– Research questions provide the basis for planning research study – design, materials, data analysis

Determined research design– Experimental, survey, correlational, descriptive

Determined methods– Subjects, materials, instruments, procedures

Next, identify data analysis procedures

Data Analysis Procedures

Excited? Apprehensive? No worries! If you’ve done a good job of the preceding 5 steps,

this should be straightforward & easy Clear research questions & design leads to stats

analysis required Work with a stats expert – identify one for your

dissertation committee Your task –have practitioner’s understanding of

appropriate analyses, how to perform PSPP analyses & how to interpret results

Can meaningful learning be enhanced by using a computer to personalize math

word problems for each student?

Common Statistical Analysis Used in Ed Tech Research