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What is the percentage of scores less than 80 if mean is 100 and standard deviation is 20?
Wiki User
∙ 12y ago
z = (80 - 100)/20 = -20/20 = -1
Look up a table of z-scores: Probability = 15.87%
Wiki User
∙ 12y ago
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What is the mean for the numbers 20 40 30 30 20 40 30 and 30?
With a mean score of 110 and a standard deviation of 18, what percentage of scores would be less than 155?
Can the mean be less than the standard deviation?
In general, a mean can be greater or less than the standard deviation.
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 If a certain statistician has an IQ of 140 what percent of the population has an IQ less than she does?
99.6% for
How would the mean and standard deviation change if the largest data in each set were removed?
Yes. The standard deviation and mean would be less. How much less would depend on the sample size, the distribution that the sample was taken from (parent distribution) and the parameters of the parent distribution. The affect on the sampling distribution of the mean and standard deviation could easily be identified by Monte Carlo simulation.
What is the difference between standard deviation and coefficient of variation?
standard deviation only measures the average deviation of the given variable from the mean whereas the coefficient of variation is = sd\mean Written as "cv" If cv>1 More variation If cv<1 and closer to 0 Less variation
What is the mean for the numbers 20 40 30 30 20 40 30 and 30?
With a mean score of 110 and a standard deviation of 18, what percentage of scores would be less than 155?
Can the mean be less than the standard deviation?
In general, a mean can be greater or less than the standard deviation.
Is it possible that the standard deviation is less than one?
Yes, a standard deviation can be less than one.
If the standard deviation is small the data is more dispersed?
No, if the standard deviation is small the data is less dispersed.
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 If a certain statistician has an IQ of 140 what percent of the population has an IQ less than she does?
99.6% for
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 if a certain statistician has an IQ of 140 what percent of the population has an IQ less than he does?
About 98% of the population.
What is an acceptable standard deviation?
An acceptable standard deviation depends entirely on the study and person asking for the study. The smaller the standard deviation, the more acceptable it will be because the less likely there are to be errors.
What percentage of scores fall below 7 if the nmean is 8 and standard deviation 2?
Assuming a normal distribution, the proportion falling between the mean (of 8) and 7 with standard deviation 2 is: z = (7 - 8) / 2 = -0.5 → 0.1915 (from normal distribution tables) → less than 7 is 0.5 - 0.1915 = 0.3085 = 0.3085 x 100 % = 30.85 % (Note: the 0.5 in the second sum is because half (0.5) of a normal distribution is less than the mean, not because 7 is half a standard deviation away from the mean, and the tables give the proportion of the normal distribution between the mean and the number of standard deviations from the mean.)
A final exam in Math 160 has a mean of 73 with standard deviation 7.8 If 24 students are randomly selected find the probability that the mean of their test scores is less than 70?
0.9699
What if I have a very high standard deviation?
The larger the value of the standard deviation, the more the data values are scattered and the less accurate any results are likely to be.
If the scores for a test have a mean of 70 and a standard deviation of 12 what percentage of scores will fall below 50?
z=-20/12 = -1.667 Assuming normal distribution, P(Z < -1.667) = 0.04779 or 4.8% of the scores should be less than 50. You can get the probabilities by looking them up on a table or use Excel, where +Normdist(50,70,12,true). My normal table has only 2 digit accuracy so for -1.67 = 0.0475.
Why in a normal distribution the distribution will be less spread out when the standard diviation of the raw scores is small?
The standard deviation (SD) is a measure of spread so small sd = small spread. So the above is true for any distribution, not just the Normal.
