# Compute test statistic for effect ratio

### Description

Computes statistic in used for inference on effect ratio in
equation (2) of Section 3.3 of Baiocchi (2010). Called by
`eff.ratio`

when finding estimate and permutation based confidence
interval for effect ratio.

### Usage

1 | ```
stat.lambda(lambda, dta, match)
``` |

### Arguments

`lambda` |
Hypothesized value of the effect ratio |

`dta` |
Data frame where first column is outcome and second column is treatment |

`match` |
Data frame where first column contains indices for those individuals encouraged into treatment by instrumental variable and second column contains indices for those individuals discouraged from treatment by instrumental variable |

### Value

Returns the value of the statistic described above

### Author(s)

Joseph Rigdon jrigdon@stanford.edu

### References

Baiocchi M, Small D, Lorch S, Rosenbaum P (2010). Building a stronger instrument in an observational study of perinatal care for premature infants. Journal of the American Statistical Association, 105(492), 1285-1296.

### See Also

`eff.ratio`

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