# sim.icc: Simulate 2-level ICC(1) values with and without level-1... In multilevel: Multilevel Functions

## Description

ICC(1) values play an important role influencing the form of relationships among variables in nested data. This simulation allows one to create data with known ICC(1) values. Multiple variables can be created both with and without level-1 correlation.

## Usage

 `1` ```sim.icc(gsize, ngrp, icc1,nitems=1,item.cor=FALSE) ```

## Arguments

 `gsize` The simulated group size. `ngrp` The simulated number of groups. `icc1` The simulated ICC(1) value. `nitems` The number of items (vectors) to simulate. `item.cor` An option to create level-1 correlation among items. Provided as a value between 0 and 1. If used, nitems must be larger than 1.

## Value

 `GRP` The grouping designator. `VAR1` The simulated value. Multiple numbered columns if nitems>1

## Author(s)

Paul Bliese [email protected]

## References

Bliese, P. D. (2000). Within-group agreement, non-independence, and reliability: Implications for data aggregation and analysis. In K. J. Klein & S. W. Kozlowski (Eds.), Multilevel Theory, Research, and Methods in Organizations (pp. 349-381). San Francisco, CA: Jossey-Bass, Inc.

`ICC1`

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18``` ``` ## Not run: set.seed(1535324) ICC.SIM<-sim.icc(gsize=10,ngrp=100,icc1=.15) ICC1(aov(VAR1~as.factor(GRP), ICC.SIM)) # 4 items with no level-1 correlation set.seed(15324) ICC.SIM<-sim.icc(gsize=10,ngrp=100,icc1=.15,nitems=4) #items with no level-1 correlation mult.icc(ICC.SIM[,2:5],ICC.SIM\$GRP) with(ICC.SIM,waba(VAR1,VAR2,GRP))\$Cov.Theorem #Examine CorrW # 4 items with a level-1 correlation of .30 set.seed(15324) ICC.SIM<-sim.icc(gsize=10,ngrp=100,icc1=.15,nitems=4, item.cor=.3) #.30 level-1 item correlations mult.icc(ICC.SIM[,2:5],ICC.SIM\$GRP) with(ICC.SIM,waba(VAR1,VAR2,GRP))\$Cov.Theorem #Examine CorrW ## End(Not run) ```

### Example output

```Loading required package: nlme
[1] 0.16681
Variable      ICC1      ICC2
1     VAR1 0.2035837 0.7188047
2     VAR2 0.1442111 0.6275778
3     VAR3 0.2229725 0.7415725
4     VAR4 0.1549414 0.6470794
RawCorr    EtaBx     EtaBy     CorrB    EtaWx     EtaWy       CorrW
1 0.07728039 0.530273 0.4775097 0.5939511 0.847827 0.8786265 -0.09815005
Variable      ICC1      ICC2
1     VAR1 0.1669452 0.6671118
2     VAR2 0.1558558 0.6486689
3     VAR3 0.1381652 0.6158502
4     VAR4 0.1715351 0.6743219
RawCorr    EtaBx     EtaBy     CorrB     EtaWx     EtaWy     CorrW
1 0.3987741 0.498367 0.4883034 0.6976093 0.8669662 0.8726739 0.3026887
```

multilevel documentation built on May 29, 2017, 5:38 p.m.