Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [standard-deviation]

In Probability and Statistics, the standard deviation of a statistical population or data set is a measure of how much variation or dispersion exists from its average value. It is defined as the square root of the variance. Use this tag alongside (statistics).

In Probability and Statistics, the standard deviation of a statistical population or data set is a measure of how much variation or dispersion exists from its average value. It is defined as the square root of the variance.

1413 questions
0
votes
0 answers

‘Symmetry’ of standard deviation

Let D be a (finite) set of data points. E.g., D might contain people’s heights, their exam results, or the temperature of an object at various times. Further, let m be D’s mean, and let s be D’s standard deviation. Then there’s a sense in which s is…
MarkOxford
  • 153
0
votes
1 answer

Random variable that is normally distributed

For a random variable that is normally distributed with a population mean of 80 and a population standard deviation =10 the probability that is simple random sample of 25 items will have a mean that is between 79 and 85
user488139
  • 1
0
votes
1 answer

Assessing normality help

I'm doing some math homework and I can't quite figure out how to solve this one. The length of time to complete a door assembly on an automobile factory assembly is normally distributed with a mean of 6.7 and a standard deviation of 2.2 minutes.…
SaraMae
  • 1
0
votes
0 answers

How can I eliminate abnormal numbers

I have a set of numbers. I want to run standard deviation on those numbers. Before running this process ,I first want to clean/eliminate numbers that are not close to most values. For example, assume that I have the numbers: 1, 2, 1, 3, 1, 4, 4, 2,…
Nir
  • 109
0
votes
0 answers

Standardising experimental errorbars. What is appropriate?

I have a 5 replicates of an experiment comparing the amount of bacteria on various surfaces. I've standardise the values because the absolute values don't mean a lot to a potential reader: $\frac{x-\bar{X}}{S}$, where $\bar{X}$ is the sample mean…
HCAI
  • 359
0
votes
1 answer

Standard Deviation

I really need help with this question. If someone could help me it would be great. A water ride has the minimum height requirement of 5 feet. The average height of children who visit the park is 4 feet 10 inches, with a standard deviation of 2…
G.Rivera
  • 9
0
votes
1 answer

Calculate standard deviation of merged sets with limited information (full details inside)

I have: A1: {3, 5, 6} and A2: {3, 4, 6, 8} Avg A1: 4.(6) Std.Deviation A1: 1.247 Avg A2: 5.25 Std. Deviation A2: 1.92 Merging A1 and A2, we get A12: {3, 3, 4, 5, 6, 6, 8} Avg A12: 5 Std. Deviation A12: 1.69 I want to be able to obtain those…
baderous
  • 15
0
votes
3 answers

How do I calculate the correct number of significant digits in the mean of a large data set?

I've recently become curious about calculating the mean, standard deviation, and uncertainty in the mean of relatively large data sets (>10,000 data points). My question is about the way to express the mean and the uncertainty when the uncertainty…
James Schrumpf
  • 1
0
votes
0 answers

How do I can confirm if the following is a high standard deviation?

If a dataset has a mean of 17 and a standard deviation of 6, is this a particularly high standard deviation from the norm? And if so, why? I have a looked at a few of the similar threads here where users have had similar problems however I have not…
James
  • 109
0
votes
2 answers

Finding range in a specific standard deviation

How would I go about calculating a specific standard deviations range? I know we have the 68-95-99.7 rule, but that's only for 1 standard deviation, 2 standard deviation and 3 standard deviation. What if I wanted .5 or 1.2 or 2.1 standard deviation…
Nack
  • 5
0
votes
0 answers

Calculation of the standard deviation. What am I doing wrong?

I have the following calculation example for the standard deviation, but somehow my result differs from the result in the Excel calculation. The example contains sample values for a portfolio calculation. Given are portfolio daily…
Katya
  • 1
0
votes
1 answer

approximate standard deviation

What is approximate standard deviation for the list of numbers: 10.4, 9.8, 10.0, 9.2, 10.5, 9.8, 9.9, 10.1, 10.4, 10.2, 10.7, 9.6? A. 2.1 B. 1.9 C. 1.75 D. 1.8 The question shows up on my kid's test recently. The standard deviation is 0.42. Why…
Big Smile
  • 17
0
votes
0 answers

Standard deviation of two items

I am doing an experiment and I measured 2 quantities (X and Y). From the samples of each quantity I calculated the uncertainty (standard deviation). I need to know the uncertainty of X/Y. What should I do?
Selva
  • 101
0
votes
1 answer

Calculating a z-score

The 2006 Statistical Abstract of the United States reports on a survey that asked a national sample of 80,000 American households about pet ownership. Suppose that one-third of all American households own a pet cat. The survey discovered that 31.6%…
Tyler
  • 115
0
votes
1 answer

By how much does the mean and standard deviation change over a certain amount?

The monthly profit of a small convenience store is a random variable with mean μ = 100 000 and standard deviation σ = 6 000. If we define Y to be the profit per year, assume that the monthly profits are independent and find: The mean of Y The…
pk.
  • 1
1 2 3 4 5 6
7
8