# Recent questions tagged standard-deviation

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What is Standard Deviation?
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What is a confidence interval?
500
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What is a population standard deviation?
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What is the coefficient of variation in statistics?
534
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What is the interquartile range in statistics?
333
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What is the standard deviation in statistics?
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What is the concept of hypothesis testing in statistics?
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What is the p-value associated with a z-score of 2.5 in a standard normal distribution?
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What is a p-value and how is it used in statistical testing?
521
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What is hypothesis testing and how is it used in statistics?
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What is the normal distribution and how is it used in statistics?
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How can we use probability to make predictions or draw conclusions from a sample of data?
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Calculate the median of the following test scores.$$\begin{array}{lllllllll}18 & 11 & 12 & 13 & 15 & 17 & 12 & 25 & 12\end{array}$$
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Calculate the mean of the following test scores.$$\begin{array}{lllllllll}11 & 12 & 12 & 12 & 13 & 15 & 17 & 18 & 25\end{array}$$
362
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What is the standard normal distribution?
348
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What is the normal distribution?
794
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A juice company sells its product in either a 48 -ounce size or a 32 -ounce size. It charges $$\ 3.90$$ for the 48 -ounce size. How much should it charge for the smaller...
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An engineer was assigned the task of calculating the average time spent by vehicles waiting at traffic signals. The signal timing (in seconds) would then be modified to r...
397
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The output of an instrument is often a waveform. With the goal of developing a numerical measure of closeness, scientists asked 11 experts to look at two waveforms on the...
250
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Is the influence of a single outlier greater on the sample range or the interquartile range? Explain.
450
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Is the influence of a single outlier greater on the mean or the median? Explain.
539
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What is the coefficient of variation?
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How is it that data from a normal distribution that is more than 2 standard deviations from the mean is 5%? It seems to contradict the 68-95-99.7 rule.
621
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If mean $$=62$$ and standard deviation $$=6$$, then what is $$P(56<x<68)=?$$
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A group of test scores has a mean of 75 and a standard deviation of 8 . If 7 points are added to every score in the group, what will happen to the mean and standard devia...
699
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Given that the mean is equal to 75 with a standard deviation of $$5.3$$ what scores belong to the middle of $$28 \%$$ of the population?
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If a population has a mean of 75 and a standard deviation of 15What is the mean of the sampling distribution for samples of size 25? What is the standard error of the sam...
843
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A restaurant claims that the waiting time of customers for service is normally distributed with a mean of 3 minutes and a standard deviation of 1 minute. The quality assu...
434
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What are confidence interval?
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How do you calculate the Coefficient of Variation and if the $$\mathrm{CV}$$ is lower what does that mean?
494
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What is the Coefficient of variation?
542
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When is standard deviation a good measure and when is it not?
540
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What is standard deviation?
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According the the U.S. Department of Education, full-time graduate students receive an average salary of \$12,800. The dean of graduate studies at a large state universit... 723 views 1 answers The mean score of 12 students is 42 with a standard deviation of 2 . If each score is increased by 2 points, what will happen to the standard deviation? DoubledDecreased... 562 views 1 answers What are Z-scores? 763 views 1 answers What is the relationship between standard deviation and standard variance? 1.2k views 1 answers Given a left-skewed distribution that has a median of 60, what conclusions can we draw about the mean and the mode of the data? 3.0k views 1 answers What is the relationship between mean and median in a normal distribution? 1.8k views 1 answers If a distribution is skewed to the right and has a median of 20, will the mean be greater than or less than 20? 1.0k views 1 answers Imagine that Jeremy took part in an examination. The test is having a mean score of 160 , and it has a standard deviation of 15 . If Jeremy's z-score is$1.20$, what woul... 707 views 1 answers What is the meaning of standard deviation? 611 views 1 answers Sally earned scores of 60, 65, 65, and 80 on 4 tests. How would scoring 100 on a fifth test affect the mean? 1.7k views 1 answers A sample of size 64 is drawn by simple random sampling from a normal population which has known variance 4 . The sample mean is$-0.45$. Test the hypothesis$\mathrm{H}_{...
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A firm investigates the length of telephone conversations of their office staff. Ten consecutive conversations had lengths, in minutes:\text { 10.7, } 9.5,11.1,7.8,11.9...
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James is a teacher in a small school is Boston. He is amused to find that his data is normally distributed, with 30 of his students taking a test which has 70 points. The...
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A random sample is taken and the sample size is $25 .$ The sample is normally distributed, the sample mean is 89 , and the standard deviation is $5.5 .$ Find a $90 \%$ co...
The mean of the medical test is $72.21$ with the standard deviation of $2.5 .$ Find a $95 \%$ confidence interval for a random sample of 25 students with the following sc...
Given $I Q$ scores are approximately normally distributed with a mean of 100 and a standard deviation of 15, the proportion of people with $I Q$ s above 130 is: