AK STAR Grade 9 Statistics & Probability Practice

Statistics & Probability skills

S-ID.1–S-ID.3

S-ID.5–S-ID.9

Standards basis

Alaska Mathematics Standards — Alaska

How the AK STAR reports it

AK STAR is Alaska’s state summative assessment, built around Alaska’s own mathematics standards rather than a national consortium framework. Its math blueprint is organized into grade-level content strands/instructional areas and an adaptive growth component aligned to MAP Growth instructional areas.

Blueprint & weighting

The blueprint gives target item counts and point ranges by grade and strand, rather than fixed percentage weights. Grades 3-5 and 6-9 each include summative item counts plus additional growth items; grade 9 has no summative Geometry strand, with Geometry reported only through growth items.

Official sources

Alaska Department of Education and Early Development
Alaska Department of Education and Early Development
Alaska Department of Education and Early Development

8 free questions · 0/0 correct

Practice playeasy

Four data sets record the number of pages read in four or five sessions. Which set has the least standard deviation?

Set A: $4, 8, 12, 16$
Set B: $6, 8, 10, 12, 14$
Set C: $7, 8, 9, 10, 11$
Set D: $2, 6, 10, 14, 18$

Set C has mean $9$ with consecutive values from $7$ to $11$ , each only one or two units from the center, giving the smallest standard deviation, about $1.4$ . Sets A, B, and D spread farther from their means.

Practice playeasy

The ages, in years, of seven students are $10\textsf{,}$ $16\textsf{,}$ $14\textsf{,}$ $8\textsf{,}$ $13\textsf{,}$ $15\textsf{,}$ and $8\textsf{.}$ Which data set has the same mean?

The original mean is $\dfrac{10 + 16 + 14 + 8 + 13 + 15 + 8}{7} = 12$ . The set $6\textsf{,}$ $8\textsf{,}$ $10\textsf{,}$ $12\textsf{,}$ $14\textsf{,}$ $16\textsf{,}$ $18$ also has mean $12$ , so the means match.

Practice playeasy

Seven game scores are $90\textsf{,}$ $70\textsf{,}$ $82\textsf{,}$ $75\textsf{,}$ $95\textsf{,}$ $60\textsf{,}$ and $88\textsf{.}$ Which data set has the same median?

In order, the original values have middle value $82$ , so the median is $82$ . The set $63\textsf{,}$ $65\textsf{,}$ $72\textsf{,}$ $82\textsf{,}$ $88\textsf{,}$ $88\textsf{,}$ $99$ also has median $82$ , so the medians match.

Practice playeasy

At trivia night, a team answered $6$ , $8$ , $7$ , and $9$ questions correctly in the first four rounds. In the fifth round, the team answered $x$ questions correctly. The mean number of correct answers per round is $8$ . What is the value of $x$ ?

Five rounds with a mean of $8$ correct answers total $5 \times 8 = 40$ . Since $6 + 8 + 7 + 9 = 30$ , $x = 40 - 30 = 10$ .

Practice playeasy

A histogram has bins 0-9: 4 values, 10-19: 7 values, 20-29: 5 values. How many data values are there in all?

Add bin frequencies: $4+7+5=16$ .

Practice playeasy

A normal distribution has mean $100$ and standard deviation $15$ . What value is 1 standard deviation above the mean?

$100 + 1\times15 = 115$ .

Practice playeasy

Find the median of $3, 7, 9$ .

When ordered least to greatest: $3, 7, 9$ . The middle value is $7$ .

Practice playmedium

Four data sets list quiz scores out of $120$ . Which set has the greatest standard deviation?

Set A: $100, 102, 104, 106$
Set B: $80, 90, 100, 110, 120$
Set C: $98, 99, 100, 101, 102$
Set D: $90, 95, 100, 105, 110$

Set B has mean $100$ with values stepping by $10$ from $80$ to $120$ , so each value is far from the center; its standard deviation is about $14.1$ . Set D has the same range but values cluster nearer the mean, and Sets A and C are tighter.