Question

Hey everyone, I need some stats help. I need help understanding this question. So anyone good in stats, plz help.. thankyou!

Answer 1

Fred is a weightlifter who can lift 800 pounds on 45% of his attempts. Which of these expressions represents the probability Fred will make 30 lifts out of 60?

N(60, .45, 30)

B(60, .45, 30)

B(30, .45, 60)

B(30, .800, 60)

N(30, .800, 60)

Answer 2

Can't help with stats now, but I just came to say nice username!

Answer 3

I have some notes on this

Answer 4

Topic 6.1 Inferential Statistics:
For instance, we use inferential statistics to try to infer from the sample data what the population might think. Or, we use inferential statistics to make judgments of the probability that an observed difference between groups is a dependable one or one that might have happened by chance in this study.
Cava definition:
The process of using samples to draw conclusions about populations. For example, statisticians may use "inferential statistics" to estimate a population value, to compare two populations, and to determine if change has occurred.
Inferential statistics uses a sample to draw conclusions about a population. It allows you to tell a lot about a population using relatively little information. For example, a pollster can predict the outcome of a national election by sampling only .001% of the population. A research scientist can make a reasonable estimate about whether the results of an experiment offer proof of a new theory or don't prove anything. But the sample must be random, and the experiment must be sound; an inference is only as good as the sample data it's based on.

Answer 5

@jdoe0001

Answer 6

Do \(N\) and \(B\) denote normal and binomial distributions, respectively?

Answer 7

I am not sure, I am just learning this concept..

Answer 8

I have been learning about binomial pdf and cdf but I am having a difficult time applying them

Answer 9

"...45% of his attempts" suggests a proportion, which would indicate that you should use the binomial distribution, not the normal. So you can eliminate options 1 and 5.

Knowing that one of the parameters used for calculating a binomial probability is the proportion (45% = 0.45), you can also eliminate option 4.

To figure out which remaining answer is correct, you absolutely need to know what \(B(a,b,c)\) means. \(a,b,c\) are parameters. I can tell that \(b\) is used to represent a given proportion (\(b=0.45\) in this case).

As for \(a\) and \(c\), I think they have to do with the total sample size (60) and the number of lifts that you want to be successful (30), but I'm not sure which one is represented by one of \(a\) or \(c\)...

Answer 10

So while this may not be of much help for this particular problem, you can directly calculate the desired probability using the density function (pdf) of the binomially distributed random variable (number of successful lifts).
\[P(X=30)=\binom{60}{30}(0.45)^{60-30}(1-0.45)^{30}\]
In general, to find the number of successful events \(k\) out of \(n\) total, each with \(p\) probability of occurring, you have
\[P(X=k)=\binom nkp^{n-k}(1-p)^k\]

Answer 11

Look your notes over to find out what \(B(a,b,c)\) literally means.

Answer 12

it is the binomial distribution right?

Answer 13

B(a,b,c) means B(n,p,x) where n is the number of trials, p is the probability of success within each trial and x is the particular number of successes. Thank you for your explanations. Super helpful.