census
collection of data from every member in the population
statistical significance is achieved when
we get a result that is very unlikely to occur by chance
formula calculation
least important factor to consider when conducting a statistical analysis of? data?
parameter vs. statistic
a numerical measurement describing some characteristic of a population
vs.
a numerical measurement describing some characteristic of a sample
discrete data
number of possible values is countable
When a car is randomly? selected, it is found to have a weight of 1873.6 kg
discrete or continuous?
continuous
discrete or continuous?
When a bus is randomly? selected, it is found to have a weight of 1876 kg
continuous
continuous data
infinite amount of possible values or decimals
nominal level
characterized by data that consist of names, labels, or categories only, and the data cannot be arranged in an ordering scheme
ordinal level
involves data that can be arranged in some order, but differences between data values either cannot be determined or are meaningless
interval level
involves data that can be arranged in order and the difference between any two data values is meaningful. However, there is no natural zero starting point
natural zero starting point
where none of the quantity is present
ratio level
the interval level with the additional property that there is also a natural zero starting point (where zero indicates that none of the quantity is present); for values at this level, differences and ratios are meaningful
what level of measurement?
temp. are: 62, 66, 70, 74, 78
interval
what level of measurement?
favorite films, type of restaurants
nominal
what level of measurement?
ratings of hotels on a scale of 0-4 stars
ordinal
what level of measurement?
blood levels of low, medium, and high
ordinal
what level of measurement?
number of houses people own
ratio
what level of measurement?
length of the side of a square in cm
ratio
What level of measurement? What is wrong
In a? survey, the favorite foods of respondents are identified as 100 for italian food, 200 for mexican food, 300 for chinese food, and 400 for anything else. The average? (mean) is calculated for 628 respondents a
nominal. numbers are insignificant, so mean is useless
What level of measurement? what is wrong
In a set of? data, car rankings are represented as 100
for first, 200 for second, and 300 for third. The average? (mean) of the 664 car rankings is 231.2 .
ordinal. data shouldnt be used to calculate an average
observational vs. experiment
dont modify vs. apply some treatment then observe its effects
What is the difference between a random sample and a simple random? sample?
With a random? sample, each individual has the same chance of being selected. With a simple random? sample, all samples of the same size have the same chance of being selected.
systematic sampling
Select some starting point and then select every kth element in the population.
stratified sampling
Subdivide the population into at least two different subgroups that share the same characteristics, then draw a sample from each subgroup
cluster sampling
Divide the population area into sections (or clusters). Then randomly select some of those clusters. Now choose all members from selected clusters
convenience sampling
Use results that are easy to get
multistage sampling
Collect data by using some combination of the basic sampling methods
3 very important considerations in the design of experiments are the following:
1. Use randomization to assign subjects to different groups.
2. Use replication by repeating the experiment on enough subjects so that effects of treatment or other factors can be clearly seen
3. Control the effects of variables by using such techniques a
confounding
occurs in an experiment when the experimenter is not able to distinguish between the effects of different factors
placebo effect
which occurs when an untreated subject reports improvement in symptoms
What type of sampling?
A woman is selected by a marketing company to participate in a paid focus group. The company says that the woman was selected because she was randomly chosen from all women in her tax bracket.
stratified
What type of sampling?
In a poll conducted by a certain research? center, 796
adults were called after their telephone numbers were randomly generated by a? computer, and 7 % were able to correctly identify the president.
random
what type of sampling?
A man experienced a tax audit. The tax department claimed that the man was audited because he was randomly selected from all the taxpayers
random
what type of sampling?
To determine customer opinion of their food quality, General Foods randomly selects 40 city blocks during a certain week and surveys all homes within the city blocks
cluster
Determine whether the sample described below is a simple random sample.
A quality control engineer selects every 15,000th light bulb that is produced.
The sample is not a simple random sample because every sample of the same size does not have the same chance of being selected
Determine whether the sample described below is a simple random sample.
In order to test for a difference in the way that workers and non-workers purchase magazines, a research institution polls exactly 945 adult workers and 945 adult non-workers randomly
The sample is not a simple random sample because every sample of size 1890 does not have the same chance of being selected
Determine whether the sample described below is a simple random sample.
In the last year, 112,472 adults got married in a county. A researcher plans to conduct a survey of 700 of those newlyweds. After obtaining a list of those who got married, he numbers
The sample is a simple random sample because every sample of size 700 has the same chance of being selected.
Determine whether the sample described below is a simple random sample. According to a lottery commission, names of potential lottery winners
are selected from a variety of different sources. Names from the list are randomly selected in a way that is equi
The sample is a simple random sample because every sample of the same size has the same chance of being selected
class width
is the difference between two consecutive lower class limits or two consecutive lower class boundaries
in a pareto chart, the bars are arranged
in descending order according to frequencies
what type of sampling?
To determine customer opinion of their food quality, General Foods randomly selects 40 city blocks during a certain week and surveys all homes within the city blocks
cluster
In a symmetric and? bell-shaped distribution
the mean, median, and mode are the same
empirical rule
� About? 68% of all values fall within 1 standard deviation of the mean.
?� About? 95% of all values fall within 2 standard deviations of the mean.
?� About? 99.7% of all values fall within 3 standard deviations of the mean.
range
very sensitive to extreme values
range rule of thumb estimates standard deviation as
s= range/4
If your score on your next statistics test is converted to a z? score, which of these z scores would you? prefer: -?2.00, -1.00, 0, 1.00,? 2.00? Why?
The z score of 2.00 is most preferable because it is 2.00 standard deviations above the mean and would correspond to the highest of the five different possible test scores.
z score
the number of standard deviations that a given value x is above or below the mean
(x- mean)/ standard deviation
Whenever a data value is less than the? mean, the corresponding z-score is
negative
In a market research survey of 2977 ?motorists, 215 said that they made an obscene gesture in the previous month. If 45 of the surveyed motorists are randomly selected without? replacement, what is the probability that none of them made an obscene gesture
.0343. 5% guideline should be applied.
45/2977 x 100--> 1.5% --> guideline should be applied
(2762/2977) ^45 --> .0343
Determine the written description of the complement of the given event.
When 15 computers are received?, at least one of them is defective.
None of them are free of defects
When five cell phones are shipped, none of them are defective. What is the written complement?
At least one of them are defective
4 requirements of binomial
1. has a fixed number of trials
2. trials must be independent
3. outcomes into 2 categories (successes, failures)
4. probability of success remains the same throughout
coefficient of variance formula
(s/mean) x 100 --> for sample
(population standard deviance/mean) x 100 --> for population
formula using mean, probability (successes), and number of trials
n x p = mean
formula for p (successes) and q (failures)
1= p + q
range rule of thumb
s= range/4
variance
square root of ((n x summation x^2) - summation (x)^2 ) / n (n-1)
z-score
z-score= (x-mean)/ standard deviation