True or False
The only value of random sampling is to achieve a representative sample.
false
The square root of the standard deviation equals the variance
false
The sum of squared deviations about the mean always equals 0.
false
For any z distribution of normally distributed scores, P50 is always equal to zero.
true
Frequency distributions, graphs, and measures of central tendency and variability are all ways of organizing data.
true
In a positively skewed distribution, the mean has a higher value than the median.
true
In order to determine cause and effect, a researcher needs to do a true experiment.
true
In science, arguments based solely on authority ( and with no supporting evidence) are worthless
true
Measurement is always approximate with a continuous variable.
true
Skewness differentially affects the three measures of central tendency more than kurtosis does
true
The area under the normal curve represents the proportion of scores that are contained in the area.
true
The mean of a set of z scores must always equal 0.
true
The mean shows the least sampling variability of any measure of central tendency.
true
The normal curve is relatively common in psychology.
true
The overall mean is a weighted mean.
true
The z distribution takes on the same shape as the raw scores.
true
When doing summation, the number above the summation sign indicates the term ending the summation and the number below indicates the beginning term.
true
a confound is an alternative explanation for an observed result
true
the independent variable is systematically manipulated by the researcher
true
the sum of all entries in a raw frequency distribution will always equal N
true
The median is less subject to sampling variation than the mean.
false
The goal of descriptive statistics is solely to summarize and organize data.
false
A normal distribution typically arises by a process of multiplying many contributing factors together.
false
About 95% of people score between -1 and +1 standard deviations about the mean on IQ tests.
false
All z scores are calculated using the median as a reference point
false
Bimodal distributions cannot be symmetrical.
false
EX^2 and (EX)^2 usually yield an identical numerical answer for a given set of numbers
false
For data that are not normally distributed, the standard deviation will sometimes be negative.
false
It is impossible to have a z score of 30.2.
false
Karl Popper argued that science progresses by proving theories true, rather than falsifying them
false
Observational studies involve the manipulation of variables by the investigator.
false
Statistics are calculated on population data, rather than sample data
false
The areas under the curve listed in Table A apply to any distribution, regardless of shape.
false
The areas under the curve listed in Table A in the back of the book apply to any distribution, regardless of shape.
false
bar graphs (opposed to histograms) should be used to show data on interval/ratio scales.
false
on a graph, the independent variable is typically shown on the y- axis.
false
ratio scales consist of qualitative different categories such as eye color
false
A discrete variable requires nominal or interval scaling.
true
A statistic is to a sample as a parameter is to a population.
true
A symmetrical distribution can have more than one mode
true
A z score designates how many standard deviations the raw score is above or below the mean.
true
A z score indicates how many standard deviations a raw score is above or below the mean of a distribution
true
According to Tufte, bar graphs and histograms usually show unwise use of data-ink.
true
Any data point in a normal distribution with a negative z score must be below the 50th percentile.
true
Central tendency describes the central location of the set of scores.
true
Data are an indispensable part of scientific method.
true
Determining the number of students in each section of introductory psychology involves the use of a ratio scale.
true