Given a t-distribution, if P(t ≥ 2.571) = 0.025, what is the probability P(t < 2.571)?

Understand the Problem

The question is asking for the probability of a t-value being less than 2.571 given that the probability of it being greater than or equal to that value is 0.025. Since probabilities sum to 1, we can find the required probability by subtracting the known probability from 1.

Answer

The probability of the t-value being less than 2.571 is $0.975$.
Answer for screen readers

The probability of the t-value being less than 2.571 is $0.975$.

Steps to Solve

  1. Identify the known probability
    We know that the probability of the t-value being greater than or equal to 2.571 is 0.025. This can be written as:
    $$ P(T \geq 2.571) = 0.025 $$

  2. Use the total probability rule
    The sum of probabilities for continuous distributions like the t-distribution equals 1. Therefore, we can express the probability of the t-value being less than 2.571 with the following equation:
    $$ P(T < 2.571) + P(T \geq 2.571) = 1 $$

  3. Substitute the known value
    We can substitute the known probability into the equation we just created:
    $$ P(T < 2.571) + 0.025 = 1 $$

  4. Solve for the unknown probability
    To find the probability of the t-value being less than 2.571, we can rearrange the equation:
    $$ P(T < 2.571) = 1 - 0.025 $$
    $$ P(T < 2.571) = 0.975 $$

The probability of the t-value being less than 2.571 is $0.975$.

More Information

This result indicates that there is a 97.5% chance of obtaining a t-value that is less than 2.571. In statistical terms, this suggests that 2.571 is a high value, sitting at the upper tail of the distribution.

Tips

A common mistake is misinterpreting the probabilities. Some may confuse the probability of being greater than or equal to a value with that of being less than. To avoid this, always remember that for any probability, the total must equal 1.

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