Exercise

# Update the Model

The current model of the WAIS-III indicated a Heywood case between perceptual organization and processing speed. To fix a highly correlated set of latent variables, you should collapse those two variables into one latent variable. You should make a `performance`

variable that combines the manifest variables for the `perceptorg`

and `processing`

latent variables.

The data has been loaded for you and is called `IQdata`

. You can view the data using `head(IQdata)`

.

Instructions

**100 XP**

- Edit the four-factor model to include one
`performance`

variable measured by`piccomp`

,`block`

,`matrixreason`

,`digsym`

, and`symbolsearch`

. - Use the
`cfa()`

function to analyze the model for any new errors. - Summarize the model to determine model fit with the standardized solution and fit indices.