Stats week 3
Which Z-score corresponds to a score that is above the mean by 2 standard deviations?
+2
A sample of n=15 scores has M=20 and s2=9. What is the sample standard deviation?
3
Which of the follwing statements is correct regarding a biased statistic? a) A biased stat occurs when the average value of a stat either underestimates or overestimates the corresponding pop parameter. b) occurs when the average value of a stat underestimates the corresponding pop parameter c)occurs when the average value of a stat is equal to the pop par d)occurs when the average value of a stat overestimates the corresponding pop parameter
A
Last week Sarah had exams in her math and spanish classes. On the math exam, the mean was u=40 with o=5, and sarah had a score of X=45. On the spanish exam, the mean was u=60 with a o=8 and A Score of X=68. For which class should Sarah expect the better grade relative to her peers in each class?Which class should she expect a better grade relative to her peers in each class? A)not enough info B)spanish C)math D) the grades should be the same because the two exam scores are in the same location.
D) the grades should be the same because the two exam scores are in the same location.
Last week tim obtained a score of X=54 on a math exam with u=60 and o=8. He also scored X=49 on an English exam with u=55 and o=3, and X=31 on psychology exam with u=37 and o=4. Which class has the worst grades relative to peers?
English
For a population, a deviation score is computed as X - σ.
FALSE
A positive deviation score indicates that a score in a distribution is less than the mean. T OR F
False
A sample that was obtained from a continuous variable consists of the following scores: 2, 5, 8, and 9. The range of these scores is 7.
False
For a population with a mean of µ = 60 and a standard deviation of σ = 4, a score of X = 56 corresponds to a z-score of z = -0.50.
False
For a sample with M = 10 and s = 2, a score of X = 13 would be considered an extreme score, far out in the tail of the distribution.
False
For a sample with M = 40 and s = 4, about 70% of the individuals will have scores between X = 32 and X = 48.
False
For a sample with a mean of M = 63 and a standard deviation of s = 5, a z-score of z = +1.40 corresponds to X = 72.
False
If a person scores X = 66 on an exam with µ = 70, they scored worse relative to others in the class if σ = 10 than if σ = 5.
False
If the population variance is 6, then the population standard deviation is σ = 36.
False
A sample with a variance of s2 = 36 has a standard deviation equal to s = 6. T OR F
TRUE
The value for the range is determined by?
The extreme scores both high and low in the distribution
A positive z-score always corresponds to a score that is greater than the mean in a distribution.
True
A sample of n = 9 scores has SS = 72. The variance for this sample is s2 = 9.
True
A score that is 6 points above the mean corresponds to a z-score of z = +0.50. For this population, the standard deviation is σ = 12.
True
A set of scores that is transformed into z-scores will result in standardized distribution of z-scores with the exact same mean of 0 and standard deviation of 1, regardless of whether the original scores are derived from a sample or population.
True
If a sample of n = 5 scores has ΣX = 10 and ΣX2 = 100, then SS = 80.
True
The range and the variance are both measures of distance.
True
The range is considered to be a relatively crude measure of variability.
True
The sample mean is unbiased because the average of all possible sample means derived for samples of a specific size is equal to the population mean.
True
The sample variance and sample standard deviation is also referred to as the estimated population variance and estimated population standard deviation, respectively.
True
To calculate the variance for a sample, SS is divided by the appropriate degrees of freedom.
True
For a population with u=40 and o=8, what is the z-score corresponding to x=34.
Z=-0.75
In N=25 games last season, the college basketball team averaged u=74 points with a standard deviation of o=6. In their final game of the season, the team scored 90 points. Based on this information, the number of points scored in the final game was? a)above average b)far above average c)above average but dont know how much d)not enough info
b)far above average
The sum of the squared deviation scores is SS=20 for a sample of n=6 scores. What is the variance for this sample?
s2=4
A set of 5 scores has SS=20. If the scores are from a sample, the sample variance is ??? If the scores comprise a population, the pop variance is?
s2=5, o2=4
If the entire population with u=60 and o=8 is transformed into Z-scores, then the distribution of z-scores will have a mean of???and a standard deviation of???
u=0, o=1
The symbol for sample variance is s.
False
Individuals that score typically to others in a population following a treatment will tend to have extreme z-scores.
False
The sample standard deviation and sample mean are examples of biased statistics.
False
The value for SS can be less than zero.
False
Transforming an entire distribution of scores into z-scores changes an originally positively skewed distribution to a negatively skewed z-score distribution.
False
A z-score of z=+3 indicates a location that is ????
Far above the mean in the extreme right-hand tail of the distribution.
Why do deviation scores have to be squared before calculating the standard deviation?
If deviation scores were not squared, then the average distance from the mean will always equal 0.
A population distribution has u=80 and o=6. In this distribution a Z-score of Z=+2.00 identifies a location? a)two below the mean b)twelve below c)twelve above d)two below
Twelve points above the mean
In a population with a mean of µ = 30 and a standard deviation of σ = 5, a score of X = 18 would be an extreme value, far out in the tail of the distribution.
True
In the context of inferential statistics, the sample variance is classified as error variance.
True
Individuals noticeably different from the population following a treatment will tend to have extreme z-scores.
True
Multiplying every score in a sample by a constant value will change the value of the standard deviation.
True
For a population with µ = 50 and σ = 10, a score of X = 55 corresponds to z = +0.50.
True
Which of the following is a consequence of increasing variability? a)the distance from one score to another tends to increase, and a single score tends to provide a less accurate representation of the entire distribution
a)the distance from one score to another tends to increase, and a single score tends to provide a less accurate representation of the entire distribution
If two individuals in different populations have identical X scores, they also must have identical z-scores.
False
In a distribution with σ = 20, a score that has a z-score of z = +0.50 is below the mean by 10 points.
False
For a population of scores, the sum of the deviation scores is equal to 0.
TRUE
Question text For a population with µ = 75 and σ = 15, about 95% of the individuals will have scores between X = 45 and X = 105.
TRUE
A z-score indicates the distance in standard deviations a score (X) falls above or below the mean of a distribution.
True
A z-score of z = -1.00 always indicates that a score is located exactly 1 standard deviation below the mean in a distribution.
True
For a distribution of scores, the location identified by z = +1.00 and the location identified by z = -1.00 are the same distance from the mean.
True
For a sample with a standard deviation of s = 3, a z-score of z = +.5 corresponds to a location that is 1.5 points above the sample mean.
True
If a person scores X = 80 on an exam with m = 75, they scored worse relative to others in the class if σ = 8 than if σ = 4.
True
One purpose of a z-score is to provide an understanding of the exact location of a score in a distribution.
True
One purpose of a z-score is to standardize a score so that it can readily be compared with scores from other distributions that also have been transformed into z-scores.
True
