z scores
the test type you use when the population is known
what is a z-test?
What is the T-Test formula
(X-M/sx/R^2n)
the formula for confidence interval?
what is CI = x bar +/- z s/square root n
what symbol does X̄ turn into when doing a proportion test?
phat p̂
the formula for a z-test
what is x bar - mu over sx/n?
What should the t-score always be?
(answer: positive)
definition of confidence interval
what is a range of values so defined that there is a specified probability that the value of a parameter lies within
when a p-value is >.05 what should you do to the null hypothesis?
Dont reject
the p-value for a z-score of -1.56
what is .0594?
what is the pvalue? StDev=.85, avg=19.72, M=19.5, N=10
(answer pvalue=.20%)
a random variable follows a normal distribution with an unknown mean and a standard deviation of 2. In a sample of 400 selected at random a sample mean of 50 was recorded. confidence interval of 97% for the average population
(50-2.17 * 2/square root 400, 50 + 2.17 * 2/square root 400) = (49.783,50,217)
what tables can you use for a hypothesis test?
Z and t
the z-score for a p-value of 0.1151
what is -1.20?
What is the pvalue?StDev= .79, avg=11.18, M=10.95, N=10
(anwer pvalue=.20%)
the average heights of a random sample of 400 people from a city is 1.75m. It is known that the heights of the population are random variables that follow a normal distribution with a variance of 0.16. with a confidence level of 90% what would the minimum sample size need to be in order for the true mean of the heights to be less than 2 cm from the sample mean?
1.65 * .4/square root of n < 0.02 square root of n/0.658 > 1/0.02 square root of n > 32.9 n > 1082.41 the sample must be at least 1,083 people
john claims that he can run a 4.5 second 40m. Sadeye tests john at the track he runs on average 4.96s for a standard deviation of 1.4 with 15 tests completed is johns claim correct?
yes johns claim is correct
when the p-value is less than 0.05
what is "reject the Ho"?
If the confidence level is 50% with a Df of 14 then what is the the P value
(answer .694)
a sample of the various prices for a particular product has been conducted in 16 stores which were selected randomly in a neighborhood of a city. The following prices were noted; 95, 108, 97,112,99,106,105,100,99,98,104,110,107,111,103,110 assuming prices of this product follow normal law of variance of 25 and an unknown mean; 1) what is the distribution of the sample mean? 2) determine the confidence interval at 95% for the population mean
1) 95+108+ 97+112+99+106+105+100+99+98+104+110+107+111+103+110/16 x bar = 104 2)B(104,5/square root of 16) N(104,1.25) z score = 1.96 104-1.96 * 1.25, 104+1.96 * 1.25) = (101.55,106.45)
A chemical lab has purchased a new machine from a company. Before they can use the machine in their research, they must ensure it is properly calibrated. The company states that the machine will start within 15 seconds on average. The chemical lab tests 30 of the machines. On average they score 12 seconds with a standard deviation of 3.6. Is their machine properly calibrated?
no there is evidence to prove that the new machine starts<15 seconds