Recent questions in Descriptive Statistics

Types Of Variables
Answered

Jorden Pace
2022-06-30

Mode
Answered

Bailee Short
2022-06-27

Let $A$ and $B$ be nonnegative constants. If we impose the prior $\pi (\theta )\propto ({\theta}^{a})((1-\theta {)}^{b})$, then what is the Bayesian posterior mode?

Types Of Variables
Answered

Lucille Cummings
2022-06-26

Z-Scores
Answered

Yesenia Sherman
2022-06-25

For example if I wanted to compare how I performed

with a 85% in a math class with mean 70 and std dev 15;

and

with a 70% in a english class with mean 50 and std dev 15;

I would use the z-score formula to calculate a relative value for two situation and use it to compare them.

However why is it not enough just to compare each classes with the mean and use this as a basis for comparison? For example

85% -70% = 15%

70% - 50% = 20%

20 > 15 therefore I must have performed better in english

I know this is incorrect but I don't understand why. thx for the help

Z-Scores
Answered

Arraryeldergox2
2022-06-25

Question

For a normal distribution with sample mean =−19 and standard deviation =6.85 find $p(-16.15\le y\le -15.27)$, where y is a random draw from the normal distribution. Round to 4 decimal places.

My answer

I obtained the z scores for both the y values −15.27 and −16.15 and their respective z scores are 0.5445 and 0.4161. The probability under the curve with a z score of 0.5445 is 0.7054 and the probability under the curve with a z score of 0.4161 is 0.6628. With those two probabilities, I obtained the difference (getting 0.0426) and I put in that answer and was told that I was wrong. Can someone give me insight as to what I'm doing wrong?

Z-Scores
Answered

flightwingsd2
2022-06-24

When exactly do I use $Z=\frac{\overline{X}-u}{\sigma}$

and when do I use $Z=\frac{\overline{X}-u}{\frac{\sigma}{\sqrt{n}}}$

I get very confused with in what situation should be using which Z calculation. Really appreciate it to have someone explain the concept

Z-Scores
Answered

George Bray
2022-06-24

Mode
Answered

freakygirl838w
2022-06-24

Mode = $l+{\displaystyle \frac{({f}_{1}-{f}_{0})h}{2{f}_{1}-{f}_{0}-{f}_{2}}}$

Where, $l=$ lower limit of the modal class,

$h=$ size of the class interval,

${f}_{1}=$ frequency of the modal class,

${f}_{0}=$ frequency of the class preceding the modal class,

${f}_{2}=$ frequency of the class succeeding the modal class.

Explain the derivation of this formula.

Types Of Variables
Answered

Dale Tate
2022-06-24

Types Of Variables
Answered

abbracciopj
2022-06-24

Types Of Variables
Answered

Sonia Gay
2022-06-21

Mode
Answered

flightwingsd2
2022-06-21

Can mode lie between mean and median?

Mode
Answered

rose2904ks
2022-06-21

Not sure how to solve this. A variable $Y$ has a lognormal distribution if $\mathrm{log}(Y)$ has a normal distribution. So I'm thinking you can solve the question by finding the mean and standard deviation of the associated normal distribution by using the given median and mode. But I don't know how to. For a normal distribution, the median and mode equal the mean, but for a lognormal distribution they evidently do not. How to use these values to find the variance?

Meta-Analysis
Answered

Yesenia Sherman
2022-06-21

Could you please recommend a book that covers (even if it is not its main topic) elementary algebra, but from an approach closer to that found in undergraduate-level books (including proofs and excluding pedagogical padding)?.

I know most of what is included in an elementary algebra course, but I want to review this area to make sure I will not miss something elementary when studying more advanced mathematics. I mainly want to review the manipulations of real and complex expressions, rather than things like what a function or a linear equation is.

Mode
Answered

George Bray
2022-06-21

So far its clear I need to derive mean and sd of normal distribution, which is underlaying for lognormal distribution where I know mode and sd. I know the equations for derivation of mean and sd:

NOTATION:

$n(x)=$ mean of normal distribution

$sd(x)=sd$ of normal distribution

$n(y)=$ mean of lognormal distribution

$sd(y)=$ sd of lognormal distribution

$mode(y)=$ mode of lognormal distribution

EQUATIONS:

$n(x)=2\ast ln(n(y))-(1/2)\ast ln(sd(y{)}^{2}+n(y{)}^{2})$

$sd(x)=-2\ast ln(n(y))+ln(sd(y{)}^{2}+n(y{)}^{2})$

$mode(y)=exp(n(y)-sd(y{)}^{2})$

Here I stuck because I cant get the equation for $n(y)$ from these equations, that I need to compute $n(x)$. So far I ended:

$mode(y)=exp(4\ast ln(n(y))-3/2\ast ln(n(y{)}^{2}-sd(y{)}^{2}))$

$mode(y{)}^{2/3}\ast sd(y{)}^{2}=n(y{)}^{2}\ast (n(y{)}^{2/3}-mode(y{)}^{2/3})$

Can anybody help me to complete this derivation?

Mode
Answered

Sarai Davenport
2022-06-20

Mode is the item that has occurred frequently - so the peak point has occurred twice - also , the extremes has occurred twice. but I take pairs (x, y)then probably I can say that the peak is the mode.

What I can't understand is the average? How the average will be the highest point. Basically, If I just consider three points - two extreme and the highest then the average will not be the highest point. So, I couldn't understand that the bell curve has the median, mode and mean equal.

Mode
Answered

gledanju0
2022-06-20

$\pi =\left(\begin{array}{cccc}1& 2& 3& 4\\ 2& 3& 4& 1\end{array}\right)$

and initialisation vector $IV=1010$. Now I to decrypt it we used the key

${\pi}^{-1}=\left(\begin{array}{cccc}1& 2& 3& 4\\ 4& 1& 2& 3\end{array}\right)$

however isn't the inverse of a permutation it written backwards? In this case shouldn't we have

${\pi}^{-1}=\left(\begin{array}{cccc}1& 2& 3& 4\\ 1& 4& 3& 2\end{array}\right)$

Why is it the first one?

When you are majoring in subjects like Engineering, Sociology, or Economics, the chances are high that you will require descriptive statistics help, which basically stands for those cases when you need to provide more than calculations or statistical data that is presented in numbers. You may also require general help with the equations, which is why the list of answers presented will help you to proceed with your challenges. You can start with the bar graphs example We also list several descriptive statistics examples that will make it easier to understand how this part of statistics and probability works. In case you need to provide a