Question

three classes wrote the same test with the following results
class a: 40 students with a x-bar of 67.8
class b: 34 students with a x-bar of 63.72
class c: 21 students with a x-bar of 70.08
calculate the overall mean mark. include 2 decimal places.
answer:

Explanation:

Step1: Calculate total marks for Class A

$\text{Total}_A = 40 \times 67.8 = 2712$

Step2: Calculate total marks for Class B

$\text{Total}_B = 34 \times 63.72 = 2166.48$

Step3: Calculate total marks for Class C

$\text{Total}_C = 21 \times 70.08 = 1471.68$

Step4: Sum all total marks

$\text{Total}_{\text{all}} = 2712 + 2166.48 + 1471.68 = 6350.16$

Step5: Calculate total number of students

$\text{Total}_{\text{students}} = 40 + 34 + 21 = 95$

Step6: Compute overall mean

$\text{Overall Mean} = \frac{6350.16}{95}$

Answer:

66.84