- StudyBlue
- California
- University of California - Los Angeles
- Psychology
- Psychology 100a
- Mcauliffe
- Psych 100A Midterm #1

Olivia R.

What are inferential statistics?

Statistics that help us make guesses/inferences about large sets of people from information gather on small sets of people

What are two essential components of descriptive statistics?

Mean and variability

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What are visual elements when describing a distribution?

Modality, Symmetry, and asymptoticness.

Where does probability really come from?

The lack of knowledge or ignorance.

What does probability depend on?

The observer and an observed event. The probability changes as the knowledge changes.

What do inferential statistics tell us?

What is likely to be true about the characteristics of populations

Does probability exist as an absolute in the world?

No! It depends on the observer and the observed event which can change for each individual based upon knowledge.

Do inferential statistics prove things to be true?

No. There is always a possibility of error.

What are the four different types of variables?

Nominal, ordinal, interval, and ratio.

How are nominal variables defined?

by name/category.There is no implied value or order.

i.e. Male, female; ethnicity; yes or no.

How are ordinal variables defined?

There is a clear order, but the size of the differences between one value and the next is not the same. (A ranking) --> Not often used in research studies.

i.e. Agree, Strongly Agree, Disagree, strongly disagree

i.e. top 5 fave foods

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How are interval variables defined?

There are equal differences between values and represent equal intervals. There is NO true zero. (0 of value does not mean 0 of thing being measured)

i.e. Temperature in degrees (F or C). 0 degrees still implies a temperature

How are ratio variables defined?

Equal intervals but have true zero.

i.e. weight, height, score, heart rate.

What are three characteristics that describe the shape of a distribution?

Modality, symmetry, and asymptoticness

What is modality?

how many modes (humps) the distribution has

What is a floor effect?

When the distribution is positively skewed meaning a majority of the values are to the left with a long right side tail.

What is a ceiling effect?

when the distribution is negatively skewed because the majority of the values are on the right with a long left side tail.

What is asymptoticness?

how far the distribution extends out from the center of the distribution. (very long tails)

What is a strong violation of asymptoticness?

when the max or min is 1 SD away from the mean.

What is a weak violation of asymptoticness?

When the max or min is 4 SD away from the mean

What are three central tendencies?

Mode, median, and mean.

What variables can mode be applied to?

nominal, ordinal, interval, and ratio

What variables can median be applied to?

ordinal, interval, and ratio.

What types of variables can mean be applied to?

Interval and ratio

What is the weakness of the median?

It is greatly affected by middle scores

What is the weakness of the mean?

It is greatly affected by extreme scores.

What are the characteristics of a normal distribution?

1. Unimodal

2. symmetric

3. asymptotic (may have weak violation)

How do we calculate a Z-Score?

Z=(X-μ)/σ

What does the Central Limit Theorem say?

1. mean distribution of scores will be the same as the mean of the mean distribution

2. mean distribution standard deviation will be √N smaller than the score distribution

3. mean distribution will become more normal with larger sample sizes

What do we call the standard deviation of the mean distribution?

Standard Error

When do we know that the distribution will be normal for sure?

When the sample size is greater than 30.

How do we calculate standard error?

σ

_{X}= σ_{X}/ √N

When do we use a t-statistic?

when we don't know the population information.

Z-Score is to standard error and T-statistic is to___?

Estimated standard error

What are the degrees of freedom for a t-statistic?

N-1

What is a confidence interval?

A range of values that is likely to contain the population mean. Estimated from a sample mean and a source of variability.

What do you need to solve a confidence interval problem?

1.the source of standard deviation (i.e. population (Z) or sample (t)?)

2. The sample mean

3. the size of the confidence interval (mostly 95%)

In confidence intervals, known population scores means use ____, known sample scores means ____.

Z score, t-stastic

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