True or False

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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


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