Compute stability of outcome rate over time

```
computeTimeStability(
studyPopulation,
sccsModel = NULL,
maxRatio = 1.25,
alpha = 0.05
)
```

- studyPopulation
An object created using the

`createStudyPopulation()`

function.- sccsModel
Optional: A fitted SCCS model as created using

`fitSccsModel()`

. If the model contains splines for seasonality and or calendar time these will be adjusted for before computing stability.- maxRatio
The maximum global ratio between the observed and expected count.

- alpha
The alpha (type 1 error) used to test for stability.

A tibble with one row and three columns: `ratio`

indicates the estimated mean ratio between observed and expected.
`p`

is the p-value against the null-hypothesis that the ratio is smaller than `maxRatio`

, and `stable`

is `TRUE`

if `p`

is greater than `alpha`

.

Computes for each month the observed and expected count, and computes the (weighted) mean ratio between the two. If
splines are used to adjust for seasonality and/or calendar time, these adjustments are taken into consideration when
considering the expected count. A one-sided p-value is computed against the null hypothesis that the ratio is smaller
than `maxRatio`

. If this p-value exceeds the specified alpha value, the series is considered stable.