# ex1923: Who Looks After the Kids? In Sleuth3: Data Sets from Ramsey and Schafer's "Statistical Sleuth (3rd Ed)"

## Description

One issue concerning the validity of the clutch volume and parental care study of `ex1031` is the selection of the bird species in the set of currently living animals. Was the selection just as good as a random sample of species from each of the groups? One way to study this for birds, at least, is to compare the numbers of species from each of the 29 orders of birds in the study with the known total number of species in each of the orders. If the selection of birds had been at random, the expected proportion of species in the study from one particular order, n, is the proportion of all species in that order (N=9,866) times the total number of species in the sample (414). That is, the expected number in each sample, if random sampling were used, is (N/9,866)x 414. Calculate the expected numbers and compare the observed numbers with them using Pearson's chi-square statistic.

## Usage

 `1` ```ex1923 ```

## Format

A data frame with 29 observations on the following 3 variables.

Order

a character variable with the name of the order

N

the known number of species in the order

n

the number of sampled species from the order

## Source

Ramsey, F.L. and Schafer, D.W. (2013). The Statistical Sleuth: A Course in Methods of Data Analysis (3rd ed), Cengage Learning.

`ex1031`
 `1` ```str(ex1923) ```