3rd Grading Review Assessment in Statistics and Probability

Grade 11 students were asked if they agree or disagree on wearing school uniform. The number of grade 11 students who agreed on wearing school uniform is a random variable. Which of the following describes a random variable?

• It is the number of grade 11 students that agreed on wearing school uniforms.

• It is any number from a survey.

• It is a variable whose value depends on the outcome of a random experiment.

• Its values are determined by probability or chance.

Answer explanation

A random variable is a variable whose value depends on the outcome of a random event. It's basically a numerical representation of the possible results from an experiment or situation with uncertain results.

An NGO (Non-Government Organization) found out that there are 85 households in Brgy. Masipag with at least 1 senior citizen. The average age of the senior citizens is 67.8 years old. What type/s of random variable/s is/are illustrated in the given situation?

• continuous

• discrete

• continuous and discrete

• none

Answer explanation

discrete - 85 households in Brgy. Masipag

discrete - at least 1 senior citizen

continuous - average age of the senior citizens is 67.8 years old.

Suppose that 2 out of 10 bags delivered by a company is damaged. If a store receives 5 of these bags, then what are the possible values of the random variable 𝑋 representing the number of damaged bags?

Answer explanation

The maximum number of damaged bags is just 2 that is why it is impossible to have more than 2 damaged bags.

Which of the following is a possible discrete probability distribution of the random variable X representing the number of returned items in an online shop?

• 
• 
• 
• 

Answer explanation

In a discrete probability distribution, the values of the random variable and probability cannot be negative and the sum of the probabilities must be equal to 1.

Given is the probability distribution of the random variable Y representing the number of grade 11 students who are tardy in class in a day. What is the probability that at least 4 students will be tardy in any given day?

• 0.11

• 0.16

• 0.27

• 0.73

In your barangay, 20% of the teenagers has 3 cellphones, 30% has 2 cellphones, and 50% has 1 cellphone. What is the expected number of cellphones that a teenager has in your barangay?

• 1.7

• 2

• 2.3

• 3

The average height of male Filipinos is 163.5 cm with standard deviation of 37.8 cm. It is normally distributed. Which of the following true?

• The median and mode are greater than 163.5 cm.

• The mean is at the center of the graph that is rectangular shape.

• The graph is bell-shaped and symmetrical with respect to the standard deviation.

• The median and mode is equal to the mean which can be found at the center of the bell-shaped graph.

Answer explanation

One of the properties of a normal distribution is that the mean, median, and mode are equal and can be located at the center of the distribution.

• 0.8531

• 0.1469

• 0.9332

• 0.0668

The mean battery life of a certain brand of smart phone is 72 hours when in use with a standard deviation of 8 hours. If the tested smart phone lasted for less than 70 hours, which would represent its probability?

Supposed that your score in the short quiz has a corresponding negative z-score. Which of the following must be true?

• Your score is the lowest.

• Your score is better than others.

• Your score is below the average.

• Your score is higher than the mean.