Statistical Methods (Psy 3400) Review-Exam 1

Determine the distribution: Attitudes toward the death penalty (assuming people's views tend to be either extremely positive or negative).

Bimodal.

When there is a (more or less) equal probability of each score in the distribution?

Bimodal.

What is the population?

Constituents of the Congressman's state.

True/False: A distribution characterized by numerous high scores and only a few low scores would be skewed to the right.

False.

True/False: A population is a subset of the units of a sample.

False.

True/False: A sample statistic with a large standard error is a more reliable estimate of a population parameter than a sample statistics with a small standard error.

False.

True/False: Converting the scores of a non-normal distribution to standard score form makes the standardized distribution normal.

False.

True/False: Generally in this class, we will use Roman letter to indicate characteristics of populations and Greek letters to indicate characteristics of samples.

False.

True/False: In an even number of n measurements ranked from smallest to largest, the median is the middle number.

False.

True/False: Interval-scale variables have an absolute zero point.

False.

True/False: It is meaningful to multiply and divide values of qualitative variables.

False.

True/False: Population characteristics are called statistics, whereas sample characteristics are called parameters.

False.

True/False: Random sampling decreases the likelihood that your sample will be representative of your population.

False.

True/False: Standardizing a normal distribution can change its shape.

False.

True/False: The area under the entire normal curve (from negative to positive infinity) is 2.0.

False.

True/False: The median is pulled out toward the tail of a skewed distribution more than the mean is.

False.

True/False: The standard deviation of a distribution is its variance squared.

False.

True/False: The standard normal distribution has a mean of 1 and a standard deviation of 0.

False.

True/False: The value of the standard deviation of the sampling distribution of the mean is always greater than the standard deviation of the population.

False.

Suppose that repeated samples were selected from a population and the sample's standard deviation was calculated for each. The distribution of these sample's standard deviations would be called the?

Sampling distribution of S.

Inferential Statistics

Procedures for drawing conclusions based on the scores collected in a research study but going beyond them.

Determine the distribution: The scores on a very easy exam on which only a few students do poorly.

Skewed to the left.

Determine the variable: Number of students in a class.

Ratio.

Determine the variable: The number of babies born to families.

Ratio.

Determine the variable: Time to complete a task.

Ratio.

Determine the variable: Weight in pounds.

Ratio.

Number of students in a class.

Ratio.

The number of babies born to families.

Ratio.

Weight in pounds.

Ratio.

Determine the distribution: Major league baseball players' salaries in the United States (note: some salaries are extremely high).

Skewed to the right.

Determine the distribution: The ages of Psychology majors taking an Introductory Psychology course.

Skewed to the right.

The standard deviation of the distribution of sample means is typically (?) than the population standard deviation.

Smaller than.

Descriptive Statistics

Used to summarize and describe a group of numbers from a research study.

What are the properties of a probability distribution?

1. Probabilities must sum to 1 and cannot be greater than 1. 2. Probabilities must be positive; cannot be negative.

The Central Limit Theorem states that the mean of the sampling distribution of the mean is equal to the population (?).

Mean.

The Central Limit Theorem tells us that as sample size increases the sampling distribution of the mean becomes?

More normally distributed with a smaller range of scores.

How do you find the mean of a probability distribution?

Multiply each event by its probability and adding them together.

When there are scores piled up on the left side of the distribution, it is?

Negatively skewed.

Academic major.

Nominal.

Blood Type.

Nominal.

Determine the variable: Academic major.

Nominal.

Determine the variable: Blood type.

Nominal.

Determine the variable: Gender.

Nominal.

Determine the variable: Type of flowers.

Nominal.

Determine the distribution: The height of undergraduate females.

Normal.

Determine the distribution: The weight of healthy full-term babies.

Normal.

Academic rank in class.

Ordinal.

Determine the variable: Academic rank in class.

Ordinal.

Determine the variable: Placement in a race (1st, 2nd, 3rd, 4th).

Ordinal.

Determine the variable: Ratings from 1-10 of owner satisfaction with their automobiles.

Ordinal.

For the following variables, mark the letter indicating what scale the variable lies on. A, B, C, D, or F on an essay exam that represented equally spaced categories of competence.

Ordinal.

Ratings from 1 to 10 of owner satisfaction with their automobiles.

Ordinal.

The sampling distribution of the mean is?

A plot of sample means drawn from a population.

When the scores are skewed to the right, this can also be called?

A positive skew.

2 Branches of Statistics

1. Descriptive Statistics 2. Inferential Statistics

When the scores are skewed to the left, this can also be called?

A negative skew.

Which of the following is the population used in the study?

All Florida residents.

A manufacturer of cellular phones has decided that an assembly line is operating satisfactorily if less than 3% of the phones produced per day are defective. To check the quality of a day's production, the company decides to randomly sample 30 phones from a day's production to test for defects. Define the population of interest to the manufacturer.

All the phones produced during the day in question.

What is not an element of descriptive statistical problems?

An inference made about the population based on the sample.

Which of the following is NOT an element of descriptive statistical problems?

An inference made about the population based on the sample.

A sample of high school teenagers reported that 85% of those sampled are interested in pursuing a college education. This statement is a(n)______________.

Descriptive Statistic.

When there are scores widely spread out in the distribution with a large average distance between the mean and the other scores?

High variance.

Scores that are further apart have a (?) variance.

High.

Degree of test anxiety (very high, high, medium, low, very low).

Interval.

Determine the variable: A, B, C, D, or F on an essay exam that represented equally spaced categories of competence.

Interval.

Determine the variable: Degree of test anxiety (high, medium or low).

Interval.

Determine the variable: Temperature.

Interval.

When all the scores are relatively close to each other in the distribution, with a smaller average distance between the mean and the other scores?

Low variance.

Scores that are closer together have a (?) variance.

Low.

What is the sample?

The 361 constituents who wrote letters.

Which piece of information does the Central Limit Theorem allow us to disregard when working with the sampling distribution of the sample mean?

The shape of the population.

The sampling distribution of the mean becomes approximately distributed only when which of the following conditions have met?

The sample size is large.

True/False: The standard deviation is an index of variability that is in the original units of the variable.

True.

What happens to the shape of the sampling distributions as the sample size increases?

They become more normal, even though the population distribution was skewed, as expected from the Central Limit Theorem.

What happens to the standard deviations of the sampling distributions as the sample size increases?

They get smaller, as expected from the Central Limit Theorem.

True/False: The standard deviation of the sampling distribution can be estimated by collecting only a single sample.

True.

True/False: The standard deviation of the sampling distribution decreases as the sample size increases.

True.

True/False: A z-score is the number of standard deviations a particular raw score is above or below the mean of the distribution from which it comes.

True.

True/False: Another name for the standard deviation of a distribution of means is the standard error of the mean.

True.

True/False: In a normal distribution, the mean, median and mode are approximately the same.

True.

True/False: In a random sample, every unit of the population has the same chance of being included in the sample.

True.

True/False: In a relative frequency histogram, the percentage or proportion of observations in a particular interval or with a particular value is plotted along the Y-axis.

True.

True/False: Inferential statistics are used to draw conclusions about a larger population from data collected on a subset of the population (a sample), whereas descriptive statistics are used to organize, summarize and describe data.

True.

True/False: It is difficult to compare raw scores from different distributions because most distributions have different central tendencies and variabilities.

True.

True/False: It is not meaningful to rank, add or multiply values of a nominal-scale variable.

True.

True/False: Our sample estimates of population parameters are more accurate and less variable if we increase N and decrease the sample standard deviation.

True.

True/False: The Central Limit Theorem is considered powerful in statistics because we can assume that the sampling distribution of the mean is normal provided that the sample size increases.

True.

True/False: The actual score value we call the median is a percentile point that has a percentile rank of 50.

True.

True/False: The area under the normal curve to the left of the mean of the distribution is .50.

True.

True/False: The best estimate of the mean of the sampling distribution of means is the sample mean.

True.

True/False: The normal distribution is unimodal and symmetric around its central tendency.

True.

True/False: The range and the standard deviation are both measures of the variability of a set of measurements.

True.

True/False: The sample mean is a more reliable estimate of the population mean as the sample size increases.

True.