(2002•浙江)红星养猪场400头猪的质量频率分布表如下,其中数据不在分点上.
(1)计算各组的频率,填在频率分布表中,并绘出频率分布直方图;
(2)从中任选一头猪,质量在65.5 kg以上的概率是多少?
0 169524 169532 169538 169542 169548 169550 169554 169560 169562 169568 169574 169578 169580 169584 169590 169592 169598 169602 169604 169608 169610 169614 169616 169618 169619 169620 169622 169623 169624 169626 169628 169632 169634 169638 169640 169644 169650 169652 169658 169662 169664 169668 169674 169680 169682 169688 169692 169694 169700 169704 169710 169718 366461
| 组别 | 频数 | 频率 |
| 45.5~50.5 | 40 | |
| 50.5~55.5 | 80 | |
| 55.5~60.5 | 160 | |
| 60.5~65.5 | 80 | |
| 65.5~70.5 | 30 | |
| 70.5~75.5 | 10 |
(2)从中任选一头猪,质量在65.5 kg以上的概率是多少?