# Confidence Interval

The average grade of 50 students senior students in a statistics class is 85 with a standard deviation of 10.2 while a group of 60 senior students got an average of 80 with a standard deviation of 8.9, can the difference in the mean grade be attributed to chance, using a 0.05 level of significance?

### Correct answer:

Tips to related online calculators

Looking for help with calculating arithmetic mean?

Looking for a statistical calculator?

Looking for a standard deviation calculator?

Looking for a statistical calculator?

Looking for a standard deviation calculator?

#### You need to know the following knowledge to solve this word math problem:

We encourage you to watch this tutorial video on this math problem: video1

## Related math problems and questions:

- A professor

A professor in a typing class found out that the average performance of an expert typist is 85 words per minute. A random sample of 16 students took the typing test and an average speed of 62 words per minute was obtained with a standard deviation of 8. C - Performance comparing

A standardized test was administered to thousands of students with a mean score of 85 and a standard deviation of 8. A random sample of 50 students were given the same test and showed an average score of 83.20. Is there evidence to show that this group ha - Standard deviation

Find standard deviation for dataset (grouped data): Age (years) No. Of Persons 0-10 15 10-20 15 20-30 23 30-40 22 40-50 25 50-60 10 60-70 5 70-80 10 - Std-deviation

Calculate standard deviation for file: 63,65,68,69,69,72,75,76,77,79,79,80,82,83,84,88,90 - Chi square

A manufacturer of phone batteries claims that his batteries' lives are approximately normally distributed with a standard deviation equal to 0.9 years. If a random sample of 10 of these batteries has a standard deviation of 1.2 years. Do you think that th - Unemployment rate

Over the last 16 years, the country's unemployment rate has changed according to the following frequency table: years of unemployment: 2 5 2 3 3 1 unemployment rate: 0.5 1 1.5 2 2.5 3 in % (percent). Determine the two-sided confidence interval for the var - Confidence interval

A food testing laboratory in Abu Dhabi has been commissioned to carry out an estimate of the amount of olive oil contained in 1-gallon tins purchased from a range of international olive oil producers. The manufacturers state that the standard deviation of - Tallest people a

As a group, the Dutch are amongst the tallest people in the world. The average Dutchman is 184 cm tall. If a normal distribution is appropriate, and the standard deviation for Dutchmen is about 8 cm, what is the percentage of Dutchmen who will be over 2 m - Average score

In a math exam, two students scored 95, six students scored 90, 3 students scored 80, and one students scored 50. What was the average score for the class? - IQ Intelligence quotient

Intelligence quotient (IQ) is a standardized score used as the output of standardized intelligence psychological tests to quantify a person's intelligence with the rest of the population (respectively to a given group). Intelligence has an approximately n - Math test

Students wrote a math test. The average number of points obtained by them was 64. Another student wrote this test for 80 points. If the teacher added his result to the original ones, the total average of all students would be 65. How many students origina - Annual income

The annual income (in thousands of $) of fifteen families is 60, 80, 90, 96, 120, 150, 200, 360, 480, 520, 1060, 1200, 1450, 2500, 7200. Calculate the harmonic and geometric mean. - Final exam

There are 5 learners in a class that has written a final exam Aleta scored 55% vera scored 36% and Sibusiso scored 88% if Thoko scored 71% and the class average was 63%. What was Davids score as a percentage? - Reverse Pythagorean theorem

Given are lengths of the sides of the triangles. Decide which one is rectangular: Δ ABC: 77 dm, 85 dm, 36 dm ... Δ DEF: 55 dm, 82 dm, 61 dm ... Δ GHI: 24 mm, 25 mm, 7 mm ... Δ JKL: 32 dm, 51 dm, 82 dm ... Δ MNO: 51 dm, 45 dm, - Level of significance

At a certain college it is estimated that 25% of the students have cars on campus. Does this seem to be a valid estimate if in random sample of 90 college students, 28 are found to have cars? Use a 0.05 level of significance. - Average height

In a class are 34 students. The average height of the students is 165 cm. What will be the average height of students in the classroom when two pupils, tall 176 cm and 170 cm, moved from this school/class? The average height in meters of all the students - SD - mean

The mean is 10 and the standard deviation is 3.5. If the data set contains 40 data values, approximately how many of the data values will fall within the range of 6.5 to 13.5?