A large car manufacturer developed a mandatory training program for its

workers in $4$ countries. In assessing the effectiveness of this program, an

operation manager designed a survey by measuring two factors:

$$ Workers$$ improved performance $($saving time, second$).$

$$ age of each worker, $21-$to$-30$ and $31-$to$-40$ age groups.

The survey measured $200$ workers$$ improved performance in each age group,

the data was listed in the Excel file. With $90\%$ confidence, can we conclude

that the training program has been more effective for age group $31-$to$-40.$

Assume the variances of the improved performance for workers $21-$to$-30$ and

$31-$to$-40$ are equal $1$

$2=2$

$2$

$.$