Stats chapter 8

df = 6 and a=0.05

1.943

Statisticians like precision in their interval estimates. A low margin of error is needed to achieve this. Which of the following supports this when selecting sample sizes?

A larger sample size reduces the margin of error.

The t distribution consists of a family of distributions where the actual shape of each one depends on the degrees of freedom, df. For lower values of df, the t distribution is similar to the z distribution. (T/F)

False

what is a necessary condition for creating confidence intervals for the population mean

Normality of the estimator

how does an interval estimator differ from a point estimator

an interval estimator provides a range of values for the population parameter whereas a point estimator provides a single value

the standard error of the sample mean is NOT affected by the

confidence

whenever we construct a confidence interval for the population mean, the margin of error includes the standard error of x_ and the:

desired level of confidence

a 95% confidence interval for the population mean implies that:

for repeated samples, 95% of the sample means will fall within an interval

alpha (a) is often referred to as the

level of significance

in order to construct a confidence interval for u, the sampling distribution of the estimator x_ must follow or approximately follow a(n) ________ distribution

normal

what is the most typical form of a calculated confidence interval

point estimate +/- margin of error

the parameter p represents the

population proportion

when estimating the population mean, the Tdf distribution is used when the

population variance is unknown

the mean and standard deviation are often used to describe ______ dat while the proportion is a descriptive measure that can also be used for ___ data

quantitative, qualitative

a confidence interval can be interpreted as a

range of values used to estimate an unknown population parameter

when the population standard deviation is unknown, the standard error for the sample mean is calculated as:

s / sq rt of n

a confidence interval narrows if the following is accomplished

the chosen confidence level decreases; the sample size increases

when constructing a confidence interval of the population mean, the factors that affect the width of the confidence interval for a given standard deviation are

the confidence level and the sample size

In an examination of holiday spending (known to be normally distributed) of a sample of 16 holiday shoppers at a local mall, an average of $54 was spent per hour of shopping. Based on the current sample, the standard deviation is equal to $21. Find a 90% confidence interval for the population mean level of spending per hour.

{44.79675, 63.20325}