1. The student in the previous example also wants to estimate the proportion of cities that have

private refuse collectors. The students wants to estimate the population proportion with the margin of error

of 0.05, prefer a level of confidence of 95%, and has no estimate for the population proportion. (so we use

the probability is 0.50 or 50%) What is the required sample size?

Questions:

1.1 Determine the formula.

1.2 Identify the value in each parameter.

1.3 The sample size is

2. The Thailand tourism official reported in year 2018, there were 3,549,150 tourists arrived to

Chiang Rai by air. This year, they want to survey the service quality level from tourists.

What is the required sample size? Use 90% confidence level.

Questions:

2.1 Determine the formula.

2.2 Identify the value in each parameter.

2.3 The sample size is

3. A student in publication administration wants to estimate the mean monthly earning of city

council members in large cities. She can tolerate a margin of error of $100 in estimating the mean. She

would also prefer to report the interval estimate with 90% level of confidence. The student found a report by

the department of labor that report a standard deviation of $1,000. What is the required sample size?

Questions:

3.1 Determine the formula.

3.2 Identify the value in each parameter.

3.3 The sample size is

4. The Thailand Management Association is studying the income of store managers in the retail

industry. A random sample of 100 managers reveals a sample of $45,420. The standard deviation of the

population is $2,050. The association would like to answers to the following questions:

What is a reasonable range of values for the population mean? The association use 90% level of confidence.

Questions:

4.1 Determine the formula.

4.2 Identify the value in each parameter.

4.3 The sample size is