Environmental Science: Numerical Questions – Statistics Sd and Sem

Dr. Manishika Jain- Join online Paper 1 intensive course. Includes tests and expected questions.

Type I – Standard Deviation

1. In a city, the daily per capita inhalation (m3) values of contaminated air over a period of 5 days are 6.3,6.3,6.2,6.4 and 5.8, respectively. The sample mean with standard deviation of the data is

1. 6.2 ± 0.02
2. 6.2 ± 0.23
3. 6.0 ± 0.15
4. 6.2 ± 0.18

Explanation: Mean =

=

=

= = 6.2

Standard Deviation =

 6.3 6.3 - 6.2 = 0.1 0.01 6.3 6.3 - 6.2 = 0.1 0.01 6.2 6.2 - 6.2 = 0 0 6.4 6.4 - 6.2 = 0.2 0.04 5.8 5.8 - 6.2 =-0.4 0.16 Σ 0.22

Type II – Standard Error of Mean

2. In random samples of 64 boats out of a total 2400 boats, the mean number of defective boats is 3.2 with a sample standard deviation 0.8. The standard error of the mean is

1. ~0.107
2. ~0.40
3. ~0.97
4. ~0.097

Explanation: Standard Error of Mean (SEM) =

=

= 0.8/8

= 0.1

Type III – Sample Size

3. If the standard deviation of a population is 20 and the standard error of mean is 4, then the sample size is:

1. 25
2. 80
3. 5
4. 100

Explanation: Standard Error of Mean (SEM) =

4 =

= 20/4 = 5

S0, n = (5) 2 = 25

Developed by: