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21 Cards in this Set
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Standard error of the sample means: 
V(xbar) = v/radical(n) S(xbar) = s/radical(n) (when v is unknown) 

Maximum or margin error of estimate: 
1. E = Z.V (xbar) 2. E = t.S (xbar) (when v is unknown) 3. E = Z.radical (P(1  P)/n) for proportion 

To calculate Z: 
1. Divide the comfidence level (CL) by 2: 2. Find the nearest value in the body of the Ztable 3. Go and find the Zvalue 

Confidence Interval of population mean: 
Xbar  E =< M =< xbar + E P  E =< Pi =< P + E 

The best estimate of the population mean is: 
The sample mean; also called point estimate 

To construct a CI: 
1. Calculate Z by using CL 2. Calculate Vxbar 3. Calculate E 4. Find the CI using M 

Interpret the CI: 
1. The limit of the CI of the population mean are (xbar  E) & (xbar + E) 2. We expect that certain% of similarly comstructed CI to contain population mean (or population proportion when P is used) 

When population SD is unknown: 
We use sample SD instead: V ===> S 

Difference between normal distribution and tdistribution: 
 Normal distribution is bellshaped  tdistribution is mound shaped 

Degree of freedom: 
df = n  1 

As n increases more than 30: 
t approaches Z 

To find t: 
1. Calculate df 2. Use CL by using the ttable 

Population distribution is normal, sampling distribution of the sample mean is: 
Normal 

Population distribution is unknown, the sampling distribution of the sample mean is: 
1. n >= 30: guaranteed as normal by CLT 2. n < 30: assume population distribution is normal ===> sampling distribution will be normal 

1. P: 2. Pi: 
1. Sample proportion 2. Population proportion 3. Binomial distribution 

Sample size (n) to estimate a population mean for Z only: 
n = (Z. V/E)^2 

3 factors to determine sample size for population mean: 
1. Margin of error (E) 2. Confidence level (to find Z) 3. Standard deviation (V) 

Sample size (n) to estimate a population proportion (P =~ Pi): 
n = P(1  P)(Z/E)^2 n = Pi(1  Pi)(Z/E)^2 

3 factors to determine the sample size for population proportion: 
1. Margin error (E) 2. Confidence level (to find Z) 3. Proportion or SD for proportion: Vp = P (1  P) 

The calculated sample size (n) should always be rounded . . . 
To the next whole number (up) 

No estimate of n: 
P = 0.5 