---
title: 15.WAIS
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
##Exercise 15.WAIS.
Referring to exercise 15.3 in Agresti, one of the WAIS subtests called *picture completion*, asks questions about 20 pictures that have one vital detail missing. It is considered a test of attention to fine detail.

The observations for 20 subjects on (x,y), where x=picture completion score(0-20) and y=symptoms of senility(1=yes):
```{r}
pictSen <-
read.table("https://asta.math.aau.dk/datasets?file=pictSen.csv",header=T)
pictSen
```

- Assume a simple logistic model and estimate the logistic regression equation.
- Why is there a significant effect of picture completion on symptoms? 
- Estimate the probability that symptoms are present when (i) x=0, (ii) x=20.
- Over what range of x-scores is the estimated probability of senility greater than 50%?
- Estimate the effect of a one-unit increase in picture completion on the odds of
  senility symptoms.
- Provide a 95% confidence interval of this effect.