Confidence Intervals
Which z-value is used for a 95% confidence interval?
1.96
A sample in which every member of the population has an equal chance of being selected.
Simple Random Sample (SRS)
In order to find the mean, standard deviation, and all summary statistics for a list of numbers, you should do this
What is stat - calc - 1 var stats
When you are describing a distribution, you should always identify these three things (S, C, S)
What are shape, center, spread
How do you analyze (interpret the results of) a test for which the p-value is less than alpha (for instance, p < .05). What would you write?
What is you reject the null hypothesis.
Calculate the margin of error for the following confidence interval:
(1.11, 3.21)
1.05
A variable that affects both the independent and dependent variables, potentially influencing the results.
What is a confounding variable
In order to calculate correlation coefficient, you should do this
Stat - Calc - Linreg
Calculate the z score given the following information. Observed value of 100, normally distributed population, mean 85, standard deviation 20.
(100-85)/20 = 0.75
Stem plots, histograms, box plots, bar graphs, dot plots and scatter plots can be used to display this kind of data.
What is quantitative data?
If you increase your n from 4 to 16, what would the effect be on your margin of error, if your previous margin of error was 2%
New margin of error would be 1% (half of the previous margin)
The population is divided into subgroups and a proportionate random sample is drawn from each subgroup.
Stratified random sample
Your data is normally distributed and you wish to find the percentile for a single observed value.
2nd - distr (vars) - normalcdf
You have a normal distribution, this many standard deviations is what 95% of the values lie within.
What are two standard deviations?
Range of the middle 50% of the values (Q3- Qi 75th percentile - 25th percentile).
What is the Inter Quartile Range
You want to estimate the mean weight of avocados in Ojai. You take a sample of 25 avocados.
T interval
Experiment design in which experimental units are presorted into groups based on some variable, and randomly assigned within those groups to determine which treatment they will receive.
Randomized block design
You want to construct a confidence interval given a sample proportion
Data is normally distributed with a mean of 22 and a sd of 8. Calculate the value that represents the 75th percentile.
27.3959
How can you find whether or not a data point is an outlier mathematically?
What is
> Q3 + 1.5(IQR)
< Q1 - 1.5(IQR)
Construct a 95% confidence interval for the following scenario:
You take a sample of 100 students and ask them if they like the new Netflix movie. 76 report that they liked the movie.
(0.67629, 0.84371)
A company wants to study the effectiveness of a new pain relief medicine. They recruit 100 volunteers with chronic pain.
Each subject takes the new pain relief medicine for a 2-week period, and a placebo for another 2-week period. Subjects don't know which pill is the actual medicine, and the order of the pills is randomly assigned for each subject. Researchers will measure the difference in the overall pain level for each subject.
Matched pairs design
You want to create a box plot on your calculator screen
2nd-stat plot-plot ON-enter-type-zoom-zoomstat
Data is normally distributed with a mean of 22 and a sd of 6. What two values represent the boundaries for the middle 80%.
14.3107 & 29.6893
You construct a 95% confidence interval for the proportion of high school students who wear Nike shoes to be (0.22, 0.41). In order for you to achieve a margin of error of no more than 0.05, what should the size of your sample be.
384.16 therefore need sample of at least 385