Statistics - math problems

Number of problems found: 360

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
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
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
Poisson distribution - daisies
The meadow behind FLD was divided into 100 equally large parts. Subsequently, it was found that there were no daisies in ten of these parts. Estimate the total number of daisies in the meadow. Assume that daisies are randomly distributed in the meadow.
Three sigma rule
The height of trees in a given stand is known to be a quantity with a normal probability distribution with a mean value of 15 m and a variance of 5 m². Determine the interval in which there will be tree heights in such a stand with a probability of 90%
Seedlings
The meadow was divided into 30 equally large parts and then it was calculated how many seedlings are in each part. It was found that there were no seedlings in six parts, five parts contained one seedling, twelve parts two seedlings and seven parts three
There
There is 5 l of water with a temperature of 20°C in the bucket. We add 3 liters of hot water. The resulting temperature will be 30°C. What was the temperature of the hot water?
A machine
A machine produces steel rods of normally distributed length; the mean length and the standard deviation being 50.0 cm and 0.5 cm respectively. The rods do not conform to safety standards if they are either shorter than 49.1 cm or longer than 50.7 cm in l
Five number summary
Find the five-number summary for these data and make a boxplot. 14,5,12,19,2,35,5,4,3,7,5,8
Average speed
The car drove on one section of the highway for half an hour at a speed of 80 km/h. Then he reduced his speed to 60km/h. It went three-quarters of an hour at a speed of 60 km/h. What was the average speed of the car?
The volleyball ball
The volleyball ball can have a circumference after inflation of at least 650 max 750 mm. What volume of air can this ball hold, if its circumference is the average of the minimum and maximum inflation of the ball.
Roxville
The temperature in Roxville decreased 15 degree in five hours. What was the average decrease in temperature per hour? Write you answer as an integer.
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
Frequency distribution
The following frequency distribution gives the time spent for fill-up at a gas station. Assume that each value in a class is equal to the midpoint of the class. Estimate the mean fill-up time for the given data. Round your answer to the nearest hundred
Workshops
The plant has three workshops. In the first workshop, produce 5 products/hour, in the second 8 products/hour, and in the third 7 products/hour. In the first workshop, they produced 240 products, in the second 400 and the third 350 products. Find the avera
Two cables
On a flat plain, 2 columns are erected vertically upwards. One is 7 m high and the other 4 m. Cables are stretched between the top of one column and the foot of the other column. At what height will the cables cross? Assume that the cables do not sag.
Twenty
Twenty swallows sit on a 10 m long telephone cable. Assume that swallows are completely randomly distributed along the line. (a) What is the probability that more than three swallows sit on a randomly selected section of cable 1 m long? (b) What is the pr
Seeds
From a box of spruce seeds with the germination of 80%, we randomly select 10 seeds and plant them. Find the median of the random variable: the number of germinating seeds.
CoG center
Find the position of the center of gravity of a system of four mass points having masses, m₁, m₂ = 2 m1, m₃ = 3 m1, and m₄ = 4 m₁, if they lie at the vertices of an isosceles tetrahedron. (in all cases, between adjacent material points, the distance
An average a day
Forest workers planted 96 trees on Monday, 120 trees on Tuesday, and 61 trees on Wednesdays. How many trees did she plant in the last day of Thursday, if she planted an average of 105 trees a day?