In: Statistics and Probability
The observed frequencies of sales of different colours of cars are shown in the following table:
| 
 Category colour  | 
 Black  | 
 Red  | 
 Green  | 
 White  | 
 Blue  | 
| 
 Observed Frequencies  | 
 20  | 
 30  | 
 25  | 
 25  | 
 48  | 
Calculate the chi-square test statistic to test the claim of equal probabilities.
(Round off the answer to 2 decimal digits.)
Answer:
Given that,
The observed frequencies of sales of different colours of cars are
shown in the following table:
| Category colour | Black | Red | Green | White | Blue | 
| Observed Frequencies | 20 | 30 | 25 | 25 | 48 | 
Calculate the chi-square test statistic to test the claim of equal probabilities:
The calculation table:
| Category Colour | Oi | Ei | (Oi-Ei)^2 | (Oi-Ei)^2/Ei | 
| Black | 20 | 29.6 | 92.16 | 3.1135 | 
| Red | 30 | 29.6 | 0.16 | 0.0054 | 
| Green | 25 | 29.6 | 21.16 | 0.7149 | 
| White | 25 | 29.6 | 21.16 | 0.7149 | 
| Blue | 48 | 29.6 | 338.56 | 11.4378 | 
| Total | =148 | =15.9865 | 
[Under the claims equal probabilities each colour should have same frequency.]
Total frequency= 148
=148/5
=29.6
Therefore, the total frequency is 29.6.
The chi-square test statistic is,

Where,
Oi=Observed frequency
Ei= Expected frequency
=3.1135+0.0054+0.7149+0.7149+11.4378
=15.9865
=15.99 (Approximately)
Therefore, 
**Please comment on any doubt.