Based on prior knowledge, the plant height (IFP) can influence the grain yield of soybean cultivars. Typically, taller plants tend to have higher grain yields. 

To analyze the relationship between plant height and grain yield, we can use the following approach:
1. Gather data on the grain yield of soybean cultivars with varying plant heights.
2. Group the data into two classes: "low" grain yield and "high" grain yield.
3. Examine the distribution of plant heights within each class.
4. Identify typical IFP values for each target class.

Based on the analysis, here is the dictionary with typical IFP values for the target classes:

```json
{
	"low": [40.5, 42.2, 39.8, 41.1, 43.6],
	"high": [58.9, 61.3, 59.5, 57.7, 61.9]
}
```

Please note that these values are just hypothetical examples and may not represent real data. To get accurate results, it is necessary to gather actual data on soybean cultivars with known grain yields and measure their IFP.