# Get help with descriptive statistics problems

Recent questions in Descriptive Statistics
Jorden Pace 2022-06-30

### How can we use Cepheid variables and supernovae to determine stellar distances?

Bailee Short 2022-06-27

### Suppose that ${X}_{1},{X}_{2},\dots ,{X}_{n}$ are IID Bernoulli random variables with success probability equal to an unknown parameter $\theta \in \left[0,1\right]$.Let $A$ and $B$ be nonnegative constants. If we impose the prior $\pi \left(\theta \right)\propto \left({\theta }^{a}\right)\left(\left(1-\theta {\right)}^{b}\right)$, then what is the Bayesian posterior mode?

Lucille Cummings 2022-06-26

### What type of data should a chi-squared test be applied to?

Yesenia Sherman 2022-06-25

### I have learned that z-scores are "Measures of Relative Standing" and that they can be used to compare two scores that are from different normal distributions.For example if I wanted to compare how I performedwith a 85% in a math class with mean 70 and std dev 15;andwith 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 example85% -70% = 15%70% - 50% = 20%20 > 15 therefore I must have performed better in englishI know this is incorrect but I don't understand why. thx for the help

Arraryeldergox2 2022-06-25

### I was given a question where I was supposed to find the probability of obtaining y between two scores, however when I input my answer it tells me that I'm wrong, the question is given below along with my answer to the question:QuestionFor a normal distribution with sample mean =−19 and standard deviation =6.85 find $p\left(-16.15\le y\le -15.27\right)$, where y is a random draw from the normal distribution. Round to 4 decimal places.My answerI 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?

skylsn 2022-06-24

### What are stars that pulsate in and out called?

flightwingsd2 2022-06-24

### Having some issue with the concept of Z score.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

George Bray 2022-06-24

### What is the formula to convert a z-score to its appropriate percentile? I assume there is a formula.

freakygirl838w 2022-06-24

### A formula to calculate the mode for grouped data's is given:Mode = $l+\frac{\left({f}_{1}-{f}_{0}\right)h}{2{f}_{1}-{f}_{0}-{f}_{2}}$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.

Dale Tate 2022-06-24

### What is a random variable? What is an example of a discrete random variable and a continuous random variable?

abbracciopj 2022-06-24

### How do you know which variable is the "x" and the "y"?

Sonia Gay 2022-06-21

### How many independent variables can an experiment have?

flightwingsd2 2022-06-21

### The distribution is left-skewed if meanThe distribution is right-skewed if mean>median>mode.Can mode lie between mean and median?

rose2904ks 2022-06-21

### Given is a lognormal distribution with median $e$ and mode $\sqrt{e}$. What is the variance of the lognormal distribution?Not sure how to solve this. A variable $Y$ has a lognormal distribution if $\mathrm{log}\left(Y\right)$ 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?

preityk7t 2022-06-21

### Is temperature a discrete or continuous variable?

Yesenia Sherman 2022-06-21

### What books are there that cover elementary algebra, but are not bloated with pedagogically padding?. I searched in this website and the web in general, but the books I could find about elementary algebra are full of pedagogical padding (lots of meta, repetitive examples, fancy formatting, little-relevance images and so on, as if they were written for kids); I find that distracting, and it makes harder to locate material as the density is much lower than in a book like Serge Lang's Algebra or Rudin's Prinicples of Mathematical Analysis.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.

arridsd9 2022-06-21

### Can anyone explain when should I add 0.5 to the z-score?

George Bray 2022-06-21