FINDINGS: books for younger kids have fewer edges, but effect goes away when you control for author in mixed effect model….but missing some data.

If you limit to books since 1975, potentially intersteing interactions between year and age.

Edges sorted by girl rating

edges sorted by age

## 
## Call:
## lm(formula = mean_edges ~ earliest_advert_level_months, data = stats_by_book)
## 
## Residuals:
##       Min        1Q    Median        3Q       Max 
## -0.039581 -0.010410 -0.000905  0.009195  0.055213 
## 
## Coefficients:
##                               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)                  4.667e-02  2.880e-03  16.203   <2e-16 ***
## earliest_advert_level_months 1.655e-04  7.332e-05   2.257   0.0249 *  
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 0.01623 on 236 degrees of freedom
##   (6 observations deleted due to missingness)
## Multiple R-squared:  0.02113,    Adjusted R-squared:  0.01698 
## F-statistic: 5.094 on 1 and 236 DF,  p-value: 0.02492
## Linear mixed model fit by REML ['lmerMod']
## Formula: mean_edges ~ earliest_advert_level_months + (1 | author)
##    Data: stats_by_book
## 
## REML criterion at convergence: -1278
## 
## Scaled residuals: 
##      Min       1Q   Median       3Q      Max 
## -2.35745 -0.46372 -0.00944  0.39628  3.06005 
## 
## Random effects:
##  Groups   Name        Variance  Std.Dev.
##  author   (Intercept) 0.0001490 0.01221 
##  Residual             0.0001276 0.01130 
## Number of obs: 238, groups:  author, 175
## 
## Fixed effects:
##                               Estimate Std. Error t value
## (Intercept)                  4.877e-02  3.034e-03  16.074
## earliest_advert_level_months 1.198e-04  7.361e-05   1.628
## 
## Correlation of Fixed Effects:
##             (Intr)
## erlst_dvr__ -0.916
## Linear mixed model fit by REML ['lmerMod']
## Formula: mean_edges ~ earliest_advert_level_months * year + (1 | author)
##    Data: stats_by_book %>% filter(year > 1975)
## 
## REML criterion at convergence: -1097.1
## 
## Scaled residuals: 
##      Min       1Q   Median       3Q      Max 
## -2.26921 -0.45143 -0.02777  0.40766  3.09373 
## 
## Random effects:
##  Groups   Name        Variance  Std.Dev.
##  author   (Intercept) 0.0001266 0.01125 
##  Residual             0.0001422 0.01192 
## Number of obs: 212, groups:  author, 159
## 
## Fixed effects:
##                                     Estimate Std. Error t value
## (Intercept)                       -4.109e-01  5.539e-01  -0.742
## earliest_advert_level_months       2.275e-02  1.405e-02   1.619
## year                               2.296e-04  2.762e-04   0.831
## earliest_advert_level_months:year -1.129e-05  7.006e-06  -1.611
## 
## Correlation of Fixed Effects:
##             (Intr) erl___ year  
## erlst_dvr__ -0.927              
## year        -1.000  0.927       
## erlst_dv__:  0.927 -1.000 -0.927
## fit warnings:
## Some predictor variables are on very different scales: consider rescaling