Description Usage Arguments Details Value References See Also Examples

Calculate the chi-squared statistic from observed and expected counts using the Litchfield and Wilcoxon (1949) approach.

1 | ```
LWchi2(obsn, expn, totn)
``` |

`obsn` |
A numeric vector of observed counts. |

`expn` |
A numeric vector of expected counts, the same length as |

`totn` |
A numeric vector of total counts possible, the same length as |

The denominator of Litchfield and Wilcoxon's (1949) chi-squared estimate
is the minimum of the `expn`

and (`totn`

- `expn`

)
following their Nomograph No. 1. This ensures that the same chi-squared
value is calculated regardless of which proportion is reported (e.g.,
affected vs. not affected).

A list of length two.
The first element is a numeric vector of length three:
`chistat`

, chi-squared statistic;
`df`

, degrees of freedom; and
`pval`

, P value.
The second element is a numeric vector the same length as `obsn`

,
containing **total** contributions to the chi-squared. To get the
**individual** contributions to the chi-squared as reported in
Litchfield and Wilcoxon (1949), divide by `totn`

.

Litchfield, JT Jr. and F Wilcoxon. 1949. A simplified method of evaluating dose-effect experiments. Journal of Pharmacology and Experimental Therapeutics 96(2):99-113. [link].

1 |

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