Question
Which of the following statements about population mean mu is false? When the population is not approximately normal and n = 30, the confidence interval is approximately X plusminus Z alpha/x [5/Squareroot n] When the population standard deviation sigma is known and n > 30, the confidence interval is approximately X plusminus Z alpha/2 sigma/Squareroot n When the population standard deviation is unknown and n > 30, the confidence interval is approximately X plusminus Z alpha/2 [5/Squareroot n] When the population is approximately normal, the confidence interval can be obtained by using t-table method.
Explanation / Answer
Answer a
Statement a is false.
When population is not normal and sample size is small < 30, z distribution should not be used.
We use the t-distribution when the sample size is small, when the underlying distribution is normal. The t distribution should not be used with small samples from populations that are not approximately normal.