Chi Squared

Chi squared table:

Columns:

1) O

2) E

3) O-E

4) (O-E)²

5) (O-E)² / E

Rows:

The variables

How to calculate degrees of freedom?

n-1

n is the number of variables

300 seeds were grown, which 292 survived, comprising of 215 tall plants, and 77 dwarf plants.

The ratio of tall : dwarf was predicted to be 3:1. Use the Chi squared test with a 5% level of significance to determine whether the data is consistent with the predicted ratio.

Column for Tall:

1) 215

2) 219

3) -4

4) 16

5) 0.073

Column for Dwarf:

1) 77

2) 73

3) 4

5) 16

6) 0.219

Add (O-E)² / E together.

0.073 + 0.219 = 0.292

d.o.f = 2-1 = 1

Successful conclusion

My calculated value of x is greater than the critical value of y at P = 0.05, therefore I reject the null hypothesis and there is a statistically significant difference between observed and expected results.

Unsuccessful conclusion

My calculated value of x is less than the critical value of y at P=0.05, therefore I accept the null hypothesis and there is no statistically significant difference between observed and expected results, and any differences I do see could be due to chance.