Sample size calculation--population is known

#1
How to check the sample size with below values
1)Average population:0.1 mil
2)CL-95%
3)MOE-0.5
4)SD-18300

please suggest the sample size calculation formula ,when population is known
 

obh

Active Member
#2
Hi Saurabh,

Do you know what is the formula for the confidence interval when you know SD?
What part of this formula is Margin Of Error?
 
#3
Hi Saurabh,

Do you know what is the formula for the confidence interval when you know SD?
What part of this formula is Margin Of Error?
Hi,

I have monthly population via which i have checked SD.

can you help calculate the sample ,when population is 0.1mil /CL:95%/CI-+-5

Regards,
Saurabh Bhardwaj
 

obh

Active Member
#8
Hi,

You are really doing a mess with the numbers... you change the numbers all the time

What is average? :0.1 , 120000, 129,517 1,290,517 ? you should put the comma every 3 digits.
what is the STD: 18300 20,914?

With a confidence level of 0.95 => α=0.05 => 1-0.05/2=0.975 => Z_0.975=1.96

You probably mean that the MOE=5% not 5. that is mean a percentage of the average.
To get an accuracy of +-5 with a standard deviation of 18300 you need a huge sample size ... 5% is a different story ...

Also is the population finite?
 
#9
Hi,

You are really doing a mess with the numbers... you change the numbers all the time

What is average? :0.1 , 120000, 129,517 1,290,517 ? you should put the comma every 3 digits.
what is the STD: 18300 20,914?

With a confidence level of 0.95 => α=0.05 => 1-0.05/2=0.975 => Z_0.975=1.96

You probably mean that the MOE=5% not 5. that is mean a percentage of the average.
To get an accuracy of +-5 with a standard deviation of 18300 you need a huge sample size ... 5% is a different story ...

Also is the population finite?
****
Thanks for your patience..yes the population is finite.

Average:129,517
STD:209,14
MOE:-5%
N=12
CL-1.96(95%)
 

obh

Active Member
#12
Hi Saurabh,

I thought the question is what is the required sample size???

commonly used:
N - population sample size, for example, id there are 10,000,000 voters in the country and you sampled 5000: N=10,000,000 n=5000.
 
#13
Hi Saurabh,

I thought the question is what is the required sample size???

commonly used:
N - population sample size, for example, id there are 10,000,000 voters in the country and you sampled 5000: N=10,000,000 n=5000.
Hi,

Yes my question is the desired sample size ,when average population is 129,517
 

obh

Active Member
#14
Can you please give more details?
What do you mean average population? The average of the population or the sample size of the population?
 
#19
So what was the problem ...?
Dear,

Let me explain you the entire scenario.

I am sharing dummy data below:

In a call center we receive approx 0.1 million calls per month.we want to conduct a survey to gauge the c-sat.

Now i want to know,how many customers should i touch in a month (desired sample) for the survey.

Mean on 12 months call volume is 0.12 million,while SD of call volume in past 12 months is 18,000.
 

obh

Active Member
#20
Okay, so the goal is to survey...

If you don't know the expect proportion you should take the worse case: Proportion=0.5
population=129,517
confidence level=0.95
MOE=0.05

sample size=385

This says that if you get the result that 0.5 (50%) of the sample prefer the green color.
The confidence interval will be 0.5±0.05 or 50% ± 5%.