Question

An ice cream parlor tracked the number of milkshakes purchased by customers over a one month period. The data table below dsplays how many milkshakes were actually purchased and their expectations for the month. Did the model predict the milkshake sales accurately? (Assume p=0.05)

APEX Question. Please help!

I'll try to attach pictures somehow

Answer 1

You need to perform a chi-square test.

χ² = Σ ( (O-E)² /E

where:
O = observed value
E = expected value
Σ = sum

χ² = (205-175)²/175 + (114-125)²/125 + (264-250)²/250
= 5.143 + 0.968 + 0.784
= 6.894

The degrees of freedom are (3-1)=2.

The χ² for DF=2 corresponds to a p-value bigger than 0.025 but smaller than 0.05, while we wanted at least χ²= 5.99 (which is the value for p=0.05).

Therefore, the correct answer is C)Yes, the χ² value was too high