STA301 Quiz No.1 Shared by Maryam

 Which of the following statements is false?
The t distribution is symmetric about zero
The t distribution is more spread out than the standard normal distribution
As the degrees of freedom get smaller, the t-distribution’s dispersion gets smaller
The t distribution is mound-shaped

 For statistical inference about the mean of a single population when the population standard deviation is unknown, the degrees for freedom for the t distribution equal n-1 because we lose one degree of freedom by using the:
Sample mean as an estimate of the population mean
Sample standard deviation as an estimate of the population standard deviation
Sample proportion as an estimate of the population proportion
Sample size as an estimate of the population size

 In testing the hypotheses Null hypothesis:  mu = 200
Alternative hypothesis:  mu less than 200 the sample mean are found to be 120. The null hypothesis:
Should be rejected
Should not be rejected
Should be rejected only if n > 30
None of the above answers is correct

For a sample of size 20 taken from a normally distributed population with standard deviation equal to 5, a 90% confidence interval for the population mean would require the use of:
t = 1.328
t = 1.729
t = 2.12
z = 1.645

 Under which of the following circumstances is it impossible to construct a confidence interval for the population mean?
A non-normal population with a large sample and an unknown population variance
A normal population with a large sample and a known population variance
Non-normal population with a small sample and an unknown population variance
A normal population with a small sample and an unknown population variance

 Suppose that a one-tail t test is being applied to find out if the population mean is less than 100. The level of significance is .05 and 25 observations were sampled. The rejection region is:
t > 1.708
t < -1. 711
t > 1.318
t < -1.316

  Which of the following is true about the t distribution?
Approaches the normal distribution as its degrees of freedom increase
Assumes the population is normally distributed
It is more spread out than the standard normal distribution
All of the above statements are true

A random sample of size 20 taken from a normally distributed population resulted in a sample variance of 32.  The lower limit of a 90% confidence interval for the population variance would be:
52.185
20.375
20.170
54.931

A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25. The upper limit of a 95% confidence interval for the population mean would equal:
77.769
72.231
72.727
77.273

Based on sample data, the 90% confidence interval limits for the population mean are LCL = 170.86   UCL = 195.42. If the 10% level of significance were used in testing the hypotheses
 Null:  mu = 201
 Alt:  mu not equal to 201, the null hypothesis:
Would be rejected
Would not be rejected
Would have to be revised
None of the above