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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?
Wiki User
∙ 15y ago
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.
Wiki User
∙ 15y ago
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When to you use a z-scores or t-scores?
T score is usually used when the sample size is below 30 and/or when the population standard deviation is unknown.
What percentage of the area falls below the mean?
The area between the mean and 1 standard deviation above or below the mean is about 0.3413 or 34.13%
If a normally distributed group of test scores have a mean of 70 and a standard deviation of 12 find the percentage of scores that will fall below 50?
X = 50 => Z = (50 - 70)/12 = -20/12 = -1.33 So prob(X < 50) = Prob(Z < -1.33...) = 0.091
How can you convert standard deviation into percentage?
There must be a formula, but in the mean time there is a handy site that does it for you. [See related link below for the converter]
What is the standard deviation of the data set given below?
A single number, such as 478912, always has a standard deviation of 0.
How do you find the standard deviation for data?
Standard deviation calculation is somewhat difficult.Please refer to the site below for more info
What is he standard deviation of the data set given below 478912?
A single number, such as 478912, always has a standard deviation of 0.
Scores on an exam are normally distributed with a mean of 76 and a standard deviation of 10 In a group of 230 tests how many students score below 66?
There are approximately 16.4% of students who score below 66 on the exam.
Can the Variance ever be smaller than standard deviation?
Yes. If the variance is less than 1, the standard deviation will be greater that the variance. For example, if the variance is 0.5, the standard deviation is sqrt(0.5) or 0.707.
What does a z score of 1.33 mean?
Suppose the random variable, X, that you are studying, has a mean = m, and standard deviation (sd) = s. Then z = 1.33 is equivalent to saying that(x - m)/s = 1.33 or that your observed value is greater than the mean by 1.33 times the sd.
How are Stanford-Binet intelligence scale results measured?
.The test has a mean, or average, standard score of 100 and a standard deviation of 16 (subtests have a mean of 50 and a standard deviation of 8). The standard deviation indicates how far above or below the norm the subject's score is.
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.)
