So we have to make denominators' numbers the same in order to sum up them all (we can sum fractions if the denominators are the same) , and we did it by cross product (that thing on the picture)

Equating by lcm (least common multiple) is the easiest way, because you might see bigger numbers on other questions, and cross product will bring much bigger numbers, so this technic might confuse you.

By the way lcm of 4 and 5 is already 20

Hope it helps!

5 0

2 years ago

A coffee company wants to make sure that their coffee is being served at the right temperature. If it is too hot, the customers

Cerrena [4.2K]

Answer:

Null hypothesis: $\mu = 65$

Alternative hypothesis: $\mu \neq 65$

$t=\frac{\bar X-\mu_o}{\frac{s}{\sqrt{n}}}$ (1)

t-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".

For this case the value of $\mu$ represent the parameter associated to the population (True average of cofee temperature)

Step-by-step explanation:

Data given and notation

$\bar X=70.2$ represent the mean height for the sample

$s$ represent the sample standard deviation for the sample

$n=20$ sample size

$\mu_o =765$ represent the value that we want to test

$\alpha$ represent the significance level for the hypothesis test.

t would represent the statistic (variable of interest)

$p_v$ represent the p value for the test (variable of interest)

State the null and alternative hypotheses.

We need to conduct a hypothesis in order to check if the true mean i equal to 70.2, the system of hypothesis would be:

Null hypothesis: $\mu = 65$

Alternative hypothesis: $\mu \neq 65$

If we analyze the size for the sample is < 30 and we don't know the population deviation so is better apply a t test to compare the actual mean to the reference value, and the statistic is given by:

$t=\frac{\bar X-\mu_o}{\frac{s}{\sqrt{n}}}$ (1)

t-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".

For this case the value of $\mu$ represent the parameter associated to the population (True average of cofee temperature)

3 0

3 years ago