1 Hw1

1.1 load data and see it

##   School Pupil   IQ Language Group_size       IQ_c School_mean Group_mean
## 1      1 17001 15.0       46         29  3.1659379    -1.51406        5.9
## 2      1 17002 14.5       45         29  2.6659379    -1.51406        5.9
## 3      1 17003  9.5       33         29 -2.3340621    -1.51406        5.9
## 4      1 17004 11.0       46         29 -0.8340621    -1.51406        5.9
## 5      1 17005  8.0       20         29 -3.8340621    -1.51406        5.9
## 6      1 17006  9.5       30         29 -2.3340621    -1.51406        5.9
##        SES_c
## 1  -4.811981
## 2 -17.811981
## 3 -12.811981
## 4  -4.811981
## 5 -17.811981
## 6 -17.811981
## 'data.frame':    2287 obs. of  9 variables:
##  $ School     : int  1 1 1 1 1 1 1 1 1 1 ...
##  $ Pupil      : int  17001 17002 17003 17004 17005 17006 17007 17008 17009 17010 ...
##  $ IQ         : num  15 14.5 9.5 11 8 9.5 9.5 13 9.5 11 ...
##  $ Language   : int  46 45 33 46 20 30 30 57 36 36 ...
##  $ Group_size : int  29 29 29 29 29 29 29 29 29 29 ...
##  $ IQ_c       : num  3.166 2.666 -2.334 -0.834 -3.834 ...
##  $ School_mean: num  -1.51 -1.51 -1.51 -1.51 -1.51 ...
##  $ Group_mean : num  5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.9 ...
##  $ SES_c      : num  -4.81 -17.81 -12.81 -4.81 -17.81 ...

1.2 model

## Linear mixed model fit by REML ['lmerMod']
## Formula: Language ~ (1 | School)
##    Data: dta
## 
## REML criterion at convergence: 16253.1
## 
## Scaled residuals: 
##      Min       1Q   Median       3Q      Max 
## -3.11618 -0.65703  0.07597  0.74128  2.50639 
## 
## Random effects:
##  Groups   Name        Variance Std.Dev.
##  School   (Intercept) 19.63    4.431   
##  Residual             64.56    8.035   
## Number of obs: 2287, groups:  School, 131
## 
## Fixed effects:
##             Estimate Std. Error t value
## (Intercept)  40.3624     0.4282   94.26
## Linear mixed model fit by REML ['lmerMod']
## Formula: Language ~ IQ_c + (1 | School)
##    Data: dta
## 
## REML criterion at convergence: 15255.8
## 
## Scaled residuals: 
##     Min      1Q  Median      3Q     Max 
## -4.0939 -0.6375  0.0579  0.7061  3.1448 
## 
## Random effects:
##  Groups   Name        Variance Std.Dev.
##  School   (Intercept)  9.602   3.099   
##  Residual             42.245   6.500   
## Number of obs: 2287, groups:  School, 131
## 
## Fixed effects:
##             Estimate Std. Error t value
## (Intercept) 40.60823    0.30819   131.8
## IQ_c         2.48759    0.07008    35.5
## 
## Correlation of Fixed Effects:
##      (Intr)
## IQ_c 0.018
  Language Language
Predictors Estimates std. Error Estimates std. Error
(Intercept) 40.36 0.43 40.61 0.31
IQ_c 2.49 0.07
Random Effects
σ2 64.56 42.24
τ00 19.63 School 9.60 School
ICC 0.23 0.19

The estimated mean of Language scores for all children is 40.61

For one point increase in IQ_c(School mean centered IQ), Language score increase by 2.49 point, on average.

About 34.57%〔=(64.56-42.24)/64.56〕 of variance in gain scores can be attributed to differences in IQ_c(School mean centered IQ) children attending different schools.

1.3 anova

## refitting model(s) with ML (instead of REML)
## Data: dta
## Models:
## m0: Language ~ (1 | School)
## m1: Language ~ IQ_c + (1 | School)
##    Df   AIC   BIC  logLik deviance  Chisq Chi Df Pr(>Chisq)    
## m0  3 16259 16276 -8126.6    16253                             
## m1  4 15260 15283 -7625.9    15252 1001.4      1  < 2.2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

2 Hw2

2.1 load data and see it

## 'data.frame':    7230 obs. of  12 variables:
##  $ size    : num  380 380 380 380 380 380 380 380 380 380 ...
##  $ lowinc  : num  40.3 40.3 40.3 40.3 40.3 40.3 40.3 40.3 40.3 40.3 ...
##  $ mobility: num  12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 ...
##  $ female  : num  0 0 0 0 0 0 0 0 0 0 ...
##  $ black   : num  0 0 0 0 0 0 0 0 0 0 ...
##  $ hispanic: num  1 1 1 0 0 0 0 0 1 1 ...
##  $ year    : num  0.5 1.5 2.5 -1.5 -0.5 0.5 1.5 2.5 -1.5 -0.5 ...
##  $ grade   : num  2 3 4 0 1 2 3 4 0 1 ...
##  $ math    : num  1.146 1.134 2.3 -1.303 0.439 ...
##  $ retained: num  0 0 0 0 0 0 0 0 0 0 ...
##  $ school  : Factor w/ 60 levels "        2020",..: 1 1 1 1 1 1 1 1 1 1 ...
##  $ cid     : Factor w/ 1721 levels "   101480302",..: 244 244 244 248 248 248 248 248 253 253 ...

2.3 model

## Linear mixed model fit by REML ['lmerMod']
## Formula: math ~ year + (1 | school/cid)
##    Data: dta2
## 
## REML criterion at convergence: 16759.4
## 
## Scaled residuals: 
##     Min      1Q  Median      3Q     Max 
## -3.8093 -0.5831 -0.0270  0.5566  6.0867 
## 
## Random effects:
##  Groups     Name        Variance Std.Dev.
##  cid:school (Intercept) 0.6699   0.8185  
##  school     (Intercept) 0.1869   0.4324  
##  Residual               0.3470   0.5891  
## Number of obs: 7230, groups:  cid:school, 1721; school, 60
## 
## Fixed effects:
##              Estimate Std. Error t value
## (Intercept) -0.780482   0.061088  -12.78
## year         0.746123   0.005396  138.26
## 
## Correlation of Fixed Effects:
##      (Intr)
## year -0.031
## Warning in checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, :
## Model failed to converge with max|grad| = 0.00321233 (tol = 0.002, component 1)
## Linear mixed model fit by REML ['lmerMod']
## Formula: math ~ (year | school/cid)
##    Data: dta2
## 
## REML criterion at convergence: 16553.9
## 
## Scaled residuals: 
##     Min      1Q  Median      3Q     Max 
## -3.2231 -0.5611 -0.0308  0.5312  5.1579 
## 
## Random effects:
##  Groups     Name        Variance Std.Dev. Corr
##  cid:school (Intercept) 0.64127  0.8008       
##             year        0.01132  0.1064   0.55
##  school     (Intercept) 0.92436  0.9614       
##             year        0.60793  0.7797   0.92
##  Residual               0.30115  0.5488       
## Number of obs: 7230, groups:  cid:school, 1721; school, 60
## 
## Fixed effects:
##             Estimate Std. Error t value
## (Intercept) -1.64424    0.05462  -30.11
## convergence code: 0
## Model failed to converge with max|grad| = 0.00321233 (tol = 0.002, component 1)
## refitting model(s) with ML (instead of REML)
## Data: dta2
## Models:
## m21: math ~ year + (1 | school/cid)
## m22: math ~ (year | school/cid)
##     Df   AIC   BIC  logLik deviance Chisq Chi Df Pr(>Chisq)    
## m21  5 16757 16792 -8373.5    16747                            
## m22  8 16566 16621 -8275.0    16550 197.1      3  < 2.2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1