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S9.2 - Confidence Intervals
Confidence Intervals for a Population Mean When the Population Standard Deviation is Unknown
12
Mathematics
Graduate
11/08/2013

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Term
t-distribution, t =
Definition
xbar - mew/(s/n^0.5)
where s = sample standard deviation
Term
The t-statistic represents
Definition
The number of sample standard errors xbar is from the population mean mew
Term
1. Properties of the t-distribution
Definition
The t-distribution is different for different degrees of freedom
Term
2. Properties of the t-distribution
Definition
The t-distribution is centered at 0 and is symmetric about 0
Term
3. Properties of the t-distribution
Definition
The area under the curve is 1. The area on either side of 0 equals 1/2
Term
4. Properties of the t-distribution
Definition
As t increases/decreases without bound, the graph approaches but never equals 0
Term
5. Properties of the t-distribution
Definition
The area in the tails of the t-distribution is a little greater than the area in the tails of the standard normal distribution
Term
6. Properties of the t-distribution
Definition
As the sample size n increases, the density curve of t gets closer to the standard normal density curve
Term
The differences between constructing CI from a population with an unknown mean mew and unknown sd sigma
Definition
1. s in place of sigma
2. t in place of z
Term
Lower bound CI =
Definition
xbar - t(alpha/2)x(s/n^0.5)
Term
Upper bound CI =
Definition
xbar + t(alpha/2)x(s/n^0.5)
Term
Nonparametric procedures
Definition
Do not require normality and the methods are resistant to outliers
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