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miss Akunina [59]
3 years ago
8

Coliform bacteria are randomly distributed in a river at an average concentration of 1 per 20cc of water. What is the variance o

f the number of Coliform bacteria in a sample of 40cc of water
Mathematics
1 answer:
Yakvenalex [24]3 years ago
6 0

Answer:

Var = 1.9

Step-by-step explanation:

Given

p = \frac{1}{20}  i.e. 1 per 20cc of water

n = 40 -- sample size

Required

The variance

This is calculated using:

Var = np(1 - p)

So, we have:

Var = 40 * \frac{1}{20} * (1 - \frac{1}{20})

Var = 40 * \frac{1}{20} * \frac{19}{20}

Var = 2 * \frac{19}{20}

Var = \frac{38}{20}

Var = 1.9

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