Their conclusions were largely founded on guesswork.是什么意思？

Their conclusions were largely founded on guesswork.

他们的结论大部份基于猜测。

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

conclusions

n. 结束( conclusion的名词复数 )，结论，推论，签订；

例句
Several conclusions could be drawn from the results described above...
从上文描述的结果中可以得出几个结论。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

largely

adv. 大部分地，主要地，大规模地，丰富地；

例句
...a research programme that has largely failed to achieve its principal aims.
在较大程度上未能实现其主要目标的研究项目

founded

adj. 有基础的；v. 创办，成立(found的过去式和过去分词)；

例句
The abbeys were founded in the 12th century by King David as a bulwark against the English...
这些修道院是12世纪大卫王用来抵御英国人而修建的堡垒。

on

prep. （表示方向）向，（表示对象）对，（表示位置）在…上，（表示时间）在…之时；adv. （放，穿，连接）上，向前，（继续）下去；adj. 活动着的情况，状态，使用着的，发生着的，计划中的；

例句
I spend a lot on expensive jewelry and clothing...
我花很多钱购买昂贵的首饰和衣服。

guesswork

n. 猜想，猜测；

例句
It was pure guesswork on our part.
这纯属我们的猜测。